Audio Recording and Tape Transfer Glossary

Author
Nick Dynice
Post date
Friday, July 31, 2026

When clients send us tapes, the same handful of words come up over and over — and they do not always mean the same thing to everybody. An engineer who came up in the 1970s, a musician who recorded on ADAT in 1996, and someone who has only ever worked in a DAW will each use "track", "stem" and "mix" a little differently. This glossary is our house definition of each term, written so you can tell us exactly what you have and exactly what you want back.

It sits alongside our longer explainers: two-track and multitrack recording, what kind of tape do I have, noise reduction decoding, and the challenges of ADAT transfers.

Every term, A–Z

Tracks, stems and takes

Track (recording track) #

A track is one individual recorded part on a multitrack machine — one microphone, one instrument, one vocal. It occupies its own narrow stripe of the tape width and can be played back, re-recorded or muted without touching the others. A 24-track 2-inch reel holds 24 of these side by side. This is the sense we mean whenever we talk about tapes and transfers, and it is not the same "track" as a song on an album.

Track (song on an album) #

Confusingly, "track" also means an individual song on a record. That usage comes from the 1950s switch from 78 RPM discs to 33 1/3 RPM LPs, when a side could suddenly hold several separated segments. We explain the collision between the two meanings in our two-track and multitrack article. When you talk to us about tapes, assume we mean the recording sense.

Multitrack #

A multitrack recording is one made on a machine that records more than two tracks at once, keeping each part on its own track so it can be balanced later. Analog multitrack widths run from cassette 4-track up through 1/2-inch, 1-inch and 2-inch reels; digital multitrack moved to ADAT and DTRS in the 1990s. A multitrack tape is not something you can casually listen to — it has to be mixed first.

Two-track (stereo) #

A two-track recording is a finished stereo mix: left channel and right channel, nothing to unpack. Stereo, two-track, two-channel, left-and-right mix, mixdown and stereo master all describe the same thing. This is what you play in a car, burn to a CD or upload to a streaming service. Full article on two-track and multitrack.

Stem #

A stem is a submix: a group of related tracks bounced down to a single file with the mix's levels, panning, EQ and effects already printed into it. Typical stems are drums, bass, guitars, keys, lead vocal and backing vocals — usually four to twelve files rather than forty. All stems start at the same timecode, so importing them into a DAW and leaving every fader at unity rebuilds the finished mix. In film and TV post the word usually means the D/M/E stems: dialogue, music and effects.

Stems vs. tracks — the difference #

Tracks are raw source recordings; stems are mixed groups of those tracks. A track is one microphone or one instrument exactly as it was captured, with no mix decisions applied. A stem is several tracks already balanced against each other and printed with the mixer's EQ, compression, panning and reverb baked in — you can change the level of "all drums", but you can no longer move the hi-hat mic relative to the kick.

This matters for what we deliver. When we transfer your multitrack tape you get tracks: one file per tape track, all sample-aligned to a common start. Stems are made afterward, by whoever mixes the material, because creating a stem requires making mix decisions. If someone asks you for "the stems" and all you have is a multitrack reel, what they actually need is the transfer first and a mix engineer second. The exception is when a reel already contains a stem mix — some sessions were printed as stems onto a fresh multitrack for exactly this reason, and the track sheet will usually say so.

Take #

A take is one continuous recorded pass at a performance. Sessions typically produce many takes of the same song, numbered as they go, and a track sheet or tape box will often list which take is on which part of the reel.

Outtake #

An outtake is a recorded take that was not used in the released version. Outtakes include alternate arrangements, false starts, different tempos, discarded solos and takes abandoned mid-song. They are frequently the most interesting material on an old reel: alternate takes and unreleased songs are exactly what gets built into reissues, box sets and archival releases, and they only exist on the original tapes. When several reels come to us with no documentation, unmarked outtakes are the usual reason a set does not line up with the finished album.

Comp (comping) #

A comp is a composite performance assembled from the best sections of multiple takes. On tape this was done by mixing several take tracks down to one free track; in a DAW it is done by editing between playlists. If your tape has three vocal tracks and a fourth labeled "vox comp", the comp is the one that was used.

Scratch track #

A scratch track is a temporary guide performance recorded only to help the other musicians play along, with the intention of replacing it later. Scratch vocals and scratch guitars are common on multitrack tapes and are often still sitting on a track that the track sheet marks as unused — one more reason we transfer every track on the reel, not just the ones that are labeled.

In the session: tracking, overdubs and punch-ins

Tracking #

Tracking is the act of recording performances onto tracks — the first stage of making a record. It can mean the whole band playing at once with each microphone going to its own track, or one player at a time building the arrangement up. Everything that ends up on a multitrack reel got there during tracking.

Overdub #

An overdub is a new part recorded onto a free track while previously recorded tracks play back in the performer's headphones. Overdubbing is what makes multitrack recording powerful: one person can play every instrument on a song by adding one track at a time.

Punch-in (and punch-out) #

A punch-in is dropping a single track into record mid-playback to replace a specific section, then dropping back out — used to fix one bad line or one wrong note without re-recording the whole performance. The moment you go into record is the punch-in, the moment you come out is the punch-out, and on analog tape it is destructive: whatever was there before is erased for good. Punches are why an otherwise clean vocal track sometimes has a faint level or tone shift on one phrase.

Slate #

A slate is a spoken announcement recorded at the head of a take identifying the song, the date and the take number. Slates are the single most useful thing on an undocumented tape — when track sheets are lost, the slates are usually how we and you work out what is on a reel.

Bouncing (ping-ponging) #

Bouncing is combining several recorded tracks onto one or two free tracks to make room for more parts. It was standard practice on cassette 4-track and 8-track machines, and it is one-way: once four drum tracks are bounced to a stereo pair, the individual drum tracks are gone. In a modern DAW, "bounce" more often just means exporting a mix to a file.

Track sheet #

A track sheet is the paper form that documents which instrument was recorded on which track, along with tape speed, operating level and any noise reduction used. It is usually a numbered grid of boxes with an instrument name written in each one, and the number of filled boxes tells you whether the reel came off a 4-, 8-, 16- or 24-track machine. Send the track sheet with your tapes — it tells us how to set up the machine before we ever thread the reel, and we use it as a reference when mixing, since it is the only record of what the tracks actually are.

Mixes: rough, final and everything between

Mix #

A mix is the finished two-track stereo version of a song, produced by balancing all the individual tracks of a multitrack recording against each other. A multitrack tape cannot be listened to in any conventional way until it has been mixed. Your home stereo, car stereo, phone and headphones, a CD, a vinyl record, a cassette, a download and every streaming service all play stereo — so if what you have is a 16- or 24-track reel, there is no way to simply press play on it. The tape has to be transferred first, and then mixed.

Making a final mix is not a trivial step. Mixing is a highly subjective art and a very competitive field, with trade organizations, magazines, technical publications, Grammy Award categories and university degree programs all dedicated to it. There are highly sought-after engineers who are famous for their mixes and who charge among the highest fees in the industry; some specialize in one genre, some work across many. It is not a button that gets pressed at the end of a transfer.

So when you send us a multitrack tape, have a plan for the mix. You might already have a professional mix engineer in mind to deliver the tracks to. You might mix it yourself in a DAW such as Pro Tools, Logic, GarageBand, Cubase, Nuendo or FL Studio. Or, if you do not have anyone in mind, you can consult us about our mixing services — we quote on mixing once the transfer is done and we can hear the material. More on who does the mixing.

Mixing (mixdown) #

Mixing is the process of turning a multitrack recording into a two-track stereo recording by balancing every track's level, EQ, panning, dynamics and effects. The resulting stereo recording is called the mixdown or the stereo mix. The word "down" refers to going down from many tracks to two. More on tracking and mixing, or see our mixing and mastering services.

Rough mix #

A rough mix is a quick, unrefined balance made during or right after tracking so people can listen to the song before it is properly mixed. Roughs were typically bounced straight to cassette, 1/4-inch or DAT at the end of a session for the band to take home. For unreleased material, the rough mix is very often the only mix that was ever made — which is why those cassettes and DATs are worth transferring even when the multitracks survive.

We also make rough mixes for transfer clients. A multitrack transfer comes back as one file per track, and if you do not have a DAW — or do not want to learn one just to find out what is on twelve reels — those files are difficult to actually listen to. A rough mix gives you a plain stereo balance of each reel so you can hear what you have, decide what is worth mixing properly, and share it with a producer or a label without anyone needing to load a 24-track session. It is not a final mix and it is not meant to be. Ask for one when you book the transfer.

Final mix #

The final mix is the approved stereo mixdown of a song — the version everyone signed off on, and the one that goes to mastering. It is also called the print master or the approved mix. If a tape box says "final", "approved" or "master mix", that reel is the top of the chain and should be handled accordingly — final mixes usually live on 1/4-inch, 1/2-inch or DAT, and are the first thing worth transferring.

Alternate mixes #

Alternate mixes are additional versions of the same song printed for specific uses. Common ones are the instrumental (no lead vocal), the a cappella (vocal only), the TV mix or TV track (full backing without the lead vocal, for live television performance), the vocal-up mix (lead vocal a decibel or two louder), the radio edit and the 7-inch or single mix. Old mix reels and DATs are frequently full of these, one after another, with only a grease-pencil note to tell them apart, which is where track splitting comes in after the transfer.

Mastering #

Mastering is the final stage after mixing, where a mastering engineer adjusts level, EQ and dynamics across all the mixed songs so they sound like one cohesive release and hit competitive loudness. It is done differently for vinyl, CD and streaming.

Sequencing #

Sequencing is putting the mastered songs into their running order with the correct gaps between them. In the tape era this meant literally cutting the master tape with a razor blade and splicing the songs back together in album order; today it is done in software, and the equivalent operation on a transferred tape is track splitting.

Master recording #

A master recording is the copy with no generations between it and the original performance. A multitrack master is the actual reel that was rolling in the room with the artist; a two-track master is the actual reel that was rolling when the mix was made. Everything else is a copy of one of those two things.

Generation loss #

Generation loss is the cumulative degradation — added hiss, lost high end, added distortion — that occurs each time analog audio is copied from one tape to another. It is why a second-generation safety copy never sounds quite like the master, and why we transfer from the earliest-generation tape you have. Digital formats do not suffer generation loss at all when the copy is made in the digital domain, which is one of the reasons they took over. That is why we pull ADAT tapes out over ADAT Lightpipe, DTRS tapes over TDIF, and DAT over S/PDIF or AES/EBU rather than through the analog outputs: the data comes off the tape and lands in the file bit-for-bit identical, with no converter and no generation in between. Going out the analog jacks instead — which is what a lot of improvised transfers do — throws that away and adds a generation for no reason.

Mono #

Mono is a single-channel recording: the same audio comes out of both speakers, with no left-right image. Records made before roughly 1958, most 78s and many early masters are mono, and we transfer mono material from discs and reels alike.

Online, offline and real time

"Online" and "offline" are two of the most overloaded words in audio and post-production. They mean at least three different things depending on who is talking.

Online (real time) #

In audio, online means happening in real time, as the audio plays. Tape transfer is inherently an online process: a 30-minute reel takes 30 minutes to play, plus setup, machine alignment and monitoring, and there is no way to run it faster. This is the single biggest reason tape transfer is billed the way it is — the machine has to play the whole tape, and an engineer has to listen to the whole tape while it does.

Offline (rendered) #

In a DAW, offline processing is anything computed faster than real time rather than played through — an offline bounce, offline pitch correction, an offline sample-rate conversion. Offline is quicker, but anything involving actual hardware, including a tape machine or an outboard noise reduction decoder, has to run online.

Offline media #

Separately, a DAW calls a file "offline" when the session references audio it can no longer find on disk. Opening an old session from a legacy system and seeing every region greyed out usually means the audio files were archived to a different volume than the session file.

Flat transfer #

A flat transfer is a transfer made with no added EQ, compression, noise reduction or "improvement" — just the tape, played on a correctly aligned machine, captured as it is. A flat transfer is the correct archival deliverable, because any processing applied during the transfer is permanent, while processing applied afterward in a DAW is not.

Flat is how we transfer by default. If you want the hiss, clicks, crackle or dropouts cleaned up, we offer restoration as a separate service for an additional fee, working from the flat capture — so you end up with both the untouched archival file and the restored version, rather than trading one for the other.

Tape, heads and machines

Tape #

Magnetic tape is a thin plastic base film coated with magnetic particles held down by a binder, with many stocks carrying a black carbon back coating to make the tape wind evenly and dissipate static. Almost everything that matters about a tape follows from those layers: the binder is what fails in sticky shed, and it is the back-coated professional stocks that are prone to it.

Width tells you the format; it does not tell you the track count. The professional widths are 1/4-inch, 1/2-inch, 1-inch and 2-inch, and any one of them could have been recorded on machines with several different head configurations — a 1/2-inch reel might be 2, 4, 8 or 16 track. Lay the reel flat and measure the height of the tape pack with a ruler to get the width; the track sheet is what tells you the track count. The model number, length and serial number printed on the box by the manufacturer say nothing about how many tracks are on it.

Thickness matters too. Standard-play stock is about 1.5 mil; long-play is 1.0 mil and double-play 0.5 mil, each thinner grade fitting more minutes on the same reel at the cost of more print-through and more fragility. Base film also changed over time: early acetate tape goes brittle and snaps cleanly, while the polyester and Mylar stock that replaced it stretches and deforms instead. Common brands you will see on the box are Ampex and Quantegy, 3M and Scotch, BASF and Agfa, Maxell and TDK — and the brand is a real clue to how the tape should be treated before it is played.

Reel #

The reel is the flanged spool the tape is wound on, and its diameter sets the running time — not the format, and not the quality. The usual sizes are 3-inch, 5-inch, 7-inch and 10.5-inch, with 12.5- and 14-inch reels turning up in broadcast and long-form work. The bigger the reel, the more tape, and the more minutes before someone has to get up and change it.

Size correlates strongly with who made the recording. 5-inch and 7-inch reels are consumer sizes and are essentially always 1/4-inch tape — home decks, radio and record dubs, family recordings. 10.5-inch is the professional size, and 1-inch and 2-inch masters come on 10.5-inch reels or larger, effectively always. If a 10.5-inch reel shows up in a box of home tapes, it is worth a closer look.

Plastic versus metal follows the same split. Consumer reels are plastic, often clear, and they warp — a bowed flange rubs the edges of the tape and can damage it. Professional reels are aluminum: rigid, heavier, and far better at protecting the tape pack, which is why studio masters are on them. The other difference is the hub. Consumer reels have a small center hole; professional 10.5-inch reels usually have the large NAB hub, which needs matching adapters on the machine. Tape wound on a bare hub with no flanges at all is a pancake and has to be mounted before it can be played.

Because diameter is about running time, the arithmetic is worth knowing: 1,200 feet on a 7-inch reel at 7.5 ips runs about 32 minutes, while 2,500 feet on a 10.5-inch reel runs about 33 minutes at 15 ips and only about 16 at 30 ips. A big professional reel recorded at a fast speed can hold less program than a small home one — which is why an album's worth of material is often several reels, and why slates and reel numbers matter so much.

Reel to reel (open reel) #

Reel to reel describes any machine where the tape runs from an exposed supply reel on the left, across the heads, onto a take-up reel on the right, threaded by hand. The other name for it is open reel, and the contrast is with cassette formats, where both reels are sealed inside a shell and the machine threads itself.

The term says nothing about width, track count, or whether a recording is professional or domestic. A reel-to-reel machine can be a 1/4-inch home deck someone used to tape the radio, or a 2-inch 24-track studio machine, or anything between — 1/2-inch and 1-inch included. So "I have reel-to-reel tapes" tells us the shape of the problem but not the format; the tape width, the reel size and the track sheet are what actually identify what you have. Our guide to working out what kind of tape you have walks through it.

In practice a reel-to-reel tape is analog, and that is what we transfer. Digital open-reel formats did exist — Sony's DASH machines and Mitsubishi's ProDigi among them — but they were rare and expensive even when new, and we do not transfer DASH or ProDigi tapes. The digital formats that actually caught on moved to sealed cassettes instead, and those we do handle: ADAT on S-VHS, DTRS on Hi8, DAT on its own shell. The upside of open reel is that everything is reachable: the tape can be inspected, cleaned, spliced, repaired and treated before it is played, which is exactly why decades-old reels are so often recoverable.

Portastudio #

Portastudio is Tascam's brand name for their cassette-based multitrack recorders, and like Xerox or Kleenex it became the generic term for the whole category. A Portastudio combined a 4-track (later 8-track) cassette recorder and a small mixer in one portable box, ran the tape at double speed for better fidelity, and used all four tracks in one direction rather than as two stereo pairs — which is exactly why a 4-track cassette will not play back properly in a normal cassette deck. It put multitrack recording within reach of anyone with a few hundred dollars, and an enormous amount of 1980s and 1990s demo, indie and home-studio material exists only on these cassettes. The form factor outlived the tape: the mixer-plus-recorder-in-one-box hard disk recorders of the 2000s were still called portastudios.

Tape head #

A tape head is the electromagnet that writes audio to, or reads audio from, the magnetic tape as it passes by. Each head has a very narrow gap where the magnetic field crosses the tape; the narrower the gap, the better the high-frequency response. On a multitrack machine each head is a stack with one gap per track, which is why a 24-track head cannot play a 16-track tape correctly — the tape width alone does not tell you the track count.

A professional machine has three heads, and the tape meets them in this order:

  • Erase head — first in the path. It floods the tape with a strong high-frequency field that scrambles whatever was there, clearing it a fraction of a second before the record head writes the new signal. It is energized only in record, which is why playing a tape back cannot erase it. On a multitrack machine erase is per track, so one track can be replaced while the others are left untouched — that is what makes a punch-in possible, and also what makes it permanent.
  • Record head — writes the audio, mixed with an inaudible high-frequency bias signal that makes the tape respond linearly instead of distorting. Its gap is wider than the playback head's, because writing and reading want opposite things.
  • Playback head — also called the repro head, last in the path, with the narrowest gap of the three. It reads the magnetized tape and turns it back into a signal, and it is the head everything gets calibrated against.

Having record and playback as separate heads is what allows off-tape monitoring: the engineer hears what actually landed on the tape, a fraction of a second behind the performance, rather than just the signal going in. Consumer decks often combine record and playback into a single head and cannot do this. The same arrangement creates a problem for overdubbing, though — the playback head sits downstream of the record head, so a musician listening to it would be hearing existing tracks late and would play late to match. The fix, which Ampex called Sel-Sync and built for Les Paul in the 1950s, is to temporarily use part of the record head as a playback head for the already-recorded tracks. Every overdub ever made on tape depends on it.

Heads wear. The gap widens and the face develops a groove where the tape has run for decades, and a worn head loses high end and drifts in azimuth — which is why the condition of the machine matters as much as the condition of the tape when a transfer is made.

Helical scan head #

A helical scan head is a set of heads mounted on a rapidly spinning drum tilted relative to the tape path, writing data in steep diagonal stripes across the tape instead of straight lines along it. Spinning the drum gives an enormous head-to-tape speed while the tape itself crawls, which is the only practical way to get the bandwidth that video and digital audio need. Every rotary-head format works this way: VHS and S-VHS (and therefore ADAT), Hi8 (and therefore DTRS), DAT and Betacam. Analog reel-to-reel and cassette machines use the opposite approach — stationary heads and tracks running longitudinally down the tape. Helical scan drums wear, and worn drums are a common reason a 1990s digital deck reports errors on a tape that is itself perfectly fine.

Azimuth #

Azimuth is the angle of the head gap relative to the tape path. If the azimuth of the machine that plays a tape does not match the machine that recorded it, the result is dull high end and phase smearing between tracks. Aligning azimuth to each tape is part of a proper transfer setup, and it is the single most common reason a home transfer sounds muffled compared to a studio one.

IPS (inches per second) #

IPS is the speed the tape moves past the head. Professional analog work is usually 15 or 30 ips, semi-pro and many home reels are 7.5 ips, and long-play consumer recordings can be 3.75 or 1.875 ips. Faster is generally cleaner and brighter; slower gets more time on a reel.

That trade-off is why consumer 1/4-inch home decks offered the slow speeds. Before cassettes took over, a home reel-to-reel was what you used to record the radio, a record, or dictation into a microphone, and for spoken word nobody cared about the top octave — they cared about fitting hours onto one reel without getting up to flip it. Dropping from 7.5 to 3.75 ips doubles the running time, and 1.875 ips doubles it again, so a 7-inch reel that holds half an hour of music at 7.5 ips holds a couple of hours of talking at the slowest setting. Speech survives that; music does not, which is why a slow-speed reel usually turns out to be a meeting, a sermon, a letter home or a family recording rather than a session.

We need to know or determine the speed before transferring, and a track sheet usually states it. Home reels almost never have one, so if the box is unlabeled we work the speed out by ear — a tape played at the wrong speed is off in pitch and tempo by an exact factor of two, which is easy to hear and easy to correct once you know to listen for it.

Test tones (alignment tones, reference tones) #

Test tones are steady sine tones — commonly 1 kHz, 10 kHz and 100 Hz at the tape's operating level — recorded at the head of a reel so a future engineer can set up a playback machine to match the machine that made the recording. Thirty seconds of tones at the start of a reel is worth more than any other documentation on the box: it tells us exactly how to set playback level and EQ, in the recording's own terms rather than by guesswork. A track sheet normally notes which tones are present and at what level.

Calibration #

Calibration is adjusting a tape machine — playback level, high- and low-frequency EQ, azimuth and bias — so it reproduces a given tape correctly, and it is done per tape, not once per day. The engineer plays the tape's own test tones and trims the machine until the meters and the response read the way they did when the tape was recorded; if the reel has no tones, calibration is set against a reference alignment tape for the correct standard and speed, then adjusted by ear. An uncalibrated transfer can be off in level and tilted in EQ while still sounding superficially fine, and that error is baked into the files forever, which is why a calibrated flat transfer and correct noise reduction decoding are worth more than any processing applied afterward.

Leader tape #

Leader tape is the non-magnetic plastic or paper tape spliced at the start, end and sometimes between songs on a reel. It protects the recorded tape, makes threading easier, and marks song boundaries visually — colored leader between songs is often how a mix reel's running order was recorded.

Splice #

A splice is a physical join in the tape, made with a diagonal cut and a piece of splicing tape, used to attach leader, edit songs together, assemble an album's running order, or repair a break. Old splices are a routine hazard in transfer work: the adhesive dries out over decades, so splices let go on the machine or leave sticky residue on the heads and guides, and we repair them before the reel is played rather than after it comes apart.

Heads-out and tails-out #

A tape is heads-out when the beginning of the program is on the outside of the reel and ready to play, and tails-out when the end is on the outside and the tape must be rewound before playing. Professional tapes were routinely stored tails-out, which makes any print-through fall after the sound instead of before it, where it is far less audible. Tails-out is also the better way to ship a reel, because a played-through pack is wound more evenly than a rewound one.

Print-through is a faint magnetic copy of a loud passage transferring to the adjacent layer of tape on the reel, heard as a ghostly pre-echo or post-echo. It develops slowly in storage and is worse on thin, long-play tape stock and at higher storage temperatures. Print-through cannot be undone, but capturing the tape at a high resolution gives a mastering engineer the best chance of working around it.

Pancake #

A pancake is tape wound on a bare hub with no flanges — no reel. Pancakes cannot be threaded as-is and have to be mounted on a proper reel before they can be played. We mount pancakes for an additional fee.

Sticky shed syndrome #

Sticky shed syndrome is the breakdown of the binder — the glue that holds the magnetic oxide particles onto the tape — causing the tape to shed oxide, squeal, and stick to the heads and guides as it plays. It affects professional back-coated formulations made from roughly the 1970s to the 1990s, notably Ampex and Quantegy and the 3M/Scotch "Master" grades, across every width from 1/4-inch to 2-inch. A tape with sticky shed can be destroyed by a single playback attempt: the oxide carrying your recording comes off on the heads. Consumer 3M/Scotch acetate stock with silicone lubricant does not get sticky shed and must not be baked. See our tape baking service, and the FAQ on whether playing a tape can ruin it.

Hydrolysis #

Hydrolysis is the chemical reaction behind sticky shed: the polyurethane binder absorbs moisture out of the air over years of storage and breaks down, turning soft and tacky. It is a function of humidity and time, which is why identical reels stored in a damp basement and a dry closet can be in completely different condition. It also explains why the fix is a drying process rather than a cleaning one.

Baking #

Baking is the treatment for sticky shed: holding the tape at a precisely controlled low temperature for a controlled number of hours so it becomes playable again. Done properly, baking does not damage the tape and does not degrade the sound quality — it does not erase anything, dull anything or change the recording in any way. All it does is stop the tape from shedding and squealing so the reel glides across the heads and the recording can finally be captured. Done at the wrong temperature it destroys the recording permanently, and the correct temperature is below what a conventional kitchen oven can even hold, which is why this is not a home project. We have baked hundreds of tapes. Digital tapes such as ADAT, DAT and DTRS use different formulations and should never be baked.

Dehydration #

Dehydration is what baking actually does — it drives the absorbed moisture back out of the binder, reversing the hydrolysis and restoring the tape's original handling for a window of time. That window is the important part: a baked tape is playable for a period after treatment and then gradually goes sticky again, so baking is done in order to transfer, not in order to store. Once the material is captured to digital files, the condition of the tape stops being a countdown.

Mold #

Mold is a white or grey growth on the tape pack, common in tapes stored in damp conditions, and it must be removed before a transfer because it will contaminate the machine and abrade the tape. We remove mold for an additional fee prior to transfer.

Noise reduction #

Noise reduction is an encode/decode system — Dolby A, B, C or SR, or dbx and dbx II — that compresses the signal while recording and expands it on playback to bury tape hiss. An encoded tape played back without the matching decoder sounds wrong: unbalanced dynamics and a distorted, exaggerated high end. A track sheet's "NR type" box is the usual way to tell. We decode all of these with calibrated hardware.

Digital formats and the connections between them

PCM #

PCM (pulse-code modulation) is the plain, uncompressed way digital audio is stored: a stream of numbers, each one a measurement of the waveform, described entirely by its sample rate and bit depth. A WAV or AIFF file is PCM, a CD is PCM, and DAT, ADAT and DTRS all carry PCM. MP3 and AAC do not — those are compressed formats that throw data away, which is why we archive to PCM and treat MP3s as an access copy.

PCM is also the name of a specific tape format, and that is usually what people mean when they hand us one. Between roughly 1979 and 1987 — after multitrack digital arrived but before DAT — the way to record digital audio was a PCM encoder, or PCM adaptor, which converted stereo audio into a black-and-white pseudo-video signal you could record onto an ordinary VHS, Betamax or U-matic deck. Play the tape back into the same box and you got digital audio out again. It was how digital master tapes for CD duplication were delivered, and plenty of professional and home studios used it for their two-track masters; radio and TV stations used it heavily, and labels sometimes serviced singles to radio on PCM tape because it beat a cassette or a 1/4-inch copy.

The practical tell: if a videocassette is filed with your audio tapes and playing it on a TV shows a flickering black-and-white pattern instead of a picture, that is not a broken video — it is a digital audio master. We transfer PCM-encoded VHS and Betamax tapes; that page lists exactly which encoders we can decode, since the format was never standardized across manufacturers.

ADAT #

ADAT (Alesis Digital Audio Tape) is an 8-track digital multitrack format introduced in 1991 that records onto standard S-VHS videocassettes. Up to sixteen machines could be synchronized for 128 tracks, though 24 tracks — three machines, three tapes — was the common studio configuration. Original ADAT machines record 16-bit at 44.1 or 48 kHz; the later Type II machines (XT, LX20, M20) record 20-bit. ADAT tape transfers and why they are getting harder.

DTRS #

DTRS (Digital Tape Recording System) is Tascam's 8-track digital multitrack format, recording onto Hi8 videocassettes. The DA-88 launched it in 1993 and was followed by the DA-38, DA-98 and the high-resolution DA-78HR and DA-98HR. Base machines record 16-bit at 44.1 or 48 kHz; the HR models go to 24-bit. Up to sixteen machines could be chained for 128 tracks. DTRS was the format of choice in a lot of post-production houses, so DTRS tapes often turn up in film and television archives. DTRS and DA-88 transfers.

HDR (hard disk recorder) #

An HDR is a standalone digital multitrack recorder that writes to an internal hard drive instead of tape — the generation that sat between ADAT/DTRS and the computer DAW, roughly 1996 to 2005. They came as rackmount units with removable drives and as mixer-style "portastudio" boxes with recorder, mixer and CD burner in one, and nearly every pro audio company shipped one: Alesis HD24, Tascam MX-2424, Mackie SDR/HDR/MDR 24-96, plus Yamaha, Roland, Korg, Fostex and Akai. Many carried ADAT optical and TDIF over from the tape generation, which is often the cleanest way to get the audio out.

No single format ever dominated, and that is the problem now. Some wrote plain WAV or AIFF; others used compressed proprietary formats and proprietary media — DVD-RAM, magneto-optical discs, data tape cartridges — that never reached wide adoption and went obsolete fast. Expansion I/O cards were sold for only a few years after each host unit shipped, so a machine can be working perfectly and still be unusable because the card it needs no longer exists at a sane price. Full rundown of the HDR formats we transfer.

SCSI #

SCSI is the drive and peripheral interface that professional audio hardware standardized on through the 1990s, and it is how data comes off an enormous amount of that era's gear — hard disk recorders, samplers, removable-cartridge drives and CD burners. It was already near the end of its life when those machines shipped, and it was replaced by USB, then by ordinary networking, then by SD cards. Recovering material from a SCSI-era machine means keeping working SCSI hosts, cables, terminators and drives on hand, which is a large part of why this kind of conversion work is specialized rather than something a current computer can do.

ADAT Lightpipe #

ADAT Lightpipe is an optical digital connection carrying eight channels of audio down a single plastic fiber cable with a TOSLINK connector. It was introduced with the ADAT machines and is still built into audio interfaces today, which is exactly why it remains the practical route for getting ADAT tracks into a modern computer. It carries eight channels at up to 48 kHz; at 88.2 and 96 kHz the S/MUX scheme splits the same pipe into four channels. Lightpipe carries audio only — no analog conversion happens, so the transfer stays bit-for-bit digital.

TDIF #

TDIF (Tascam Digital Interface Format) is the DTRS equivalent of Lightpipe: eight channels of digital audio over a single 25-pin D-sub cable. Unlike Lightpipe, one TDIF cable is bidirectional — it carries eight channels in and eight channels out simultaneously. TDIF cables are a specific wired-for-audio type; a SCSI or parallel cable with the same connector will not work and can cause errors. Cable runs are short, around 5 metres maximum. Finding working TDIF cables and an interface that still accepts them is a real part of what makes DTRS transfers a specialist job today.

S/PDIF #

S/PDIF (Sony/Philips Digital Interface) is a two-channel digital audio connection over either a coaxial cable with an RCA connector or an optical TOSLINK cable. It is the consumer counterpart to the professional AES/EBU standard and it is the connection you will find on DAT decks, MiniDisc decks, CD players and most audio interfaces. Note that S/PDIF optical and ADAT Lightpipe use the same TOSLINK connector but carry completely different data — two channels versus eight — which is a classic source of confusion when patching an old digital rig together.

AES/EBU #

AES/EBU (AES3) is the professional two-channel digital audio standard, carried on a balanced 110-ohm cable with XLR connectors. Same job as S/PDIF, more robust over long runs, and standard on professional DAT machines and converters.

Word clock #

Word clock is a dedicated timing reference distributed over 75-ohm coaxial BNC cable so that every digital device in a chain starts each sample at exactly the same instant. Without a common clock, digital transfers produce clicks, pops and dropouts. In a multi-machine ADAT or DTRS transfer, getting the clock right is as important as getting the audio connections right.

Word clock solves a problem that long predates digital audio, and the clearest analog ancestor is the Nagra pilot tone. On location film shoots the Nagra recorder was not physically connected to the camera, so it recorded a 50 or 60 Hz reference tone — taken from the camera's motor, or later from a crystal oscillator in each machine — onto the tape alongside the audio. Nagra's Neopilot scheme put it on two narrow tracks down the middle of the 1/4-inch tape, recorded out of phase with each other so that a normal playback head cancelled them and the tone stayed inaudible under the dialogue.

At transfer time the tape was played into a resolver, which compared the recorded pilot against a studio reference and continuously trimmed the playback machine's speed so the audio ran back at exactly the rate the camera had run at. That is called resolving, and it is the same job word clock does for digital audio — the differences are that the reference arrives down a cable instead of off the tape, and the precision is per sample instead of per cycle.

The useful distinction is rate versus position. Pilot tone, word clock and FSK are rate references: they keep machines running at the same speed but say nothing about where you are in the program, which is why film sound still needed a clapperboard — the visual cousin of the slate — to mark the sync point. SMPTE timecode is what carries actual position, and later Nagras recorded it instead of pilot. A tape can need both. If you have Nagra or other location field reels, tell us what is on the pilot track and at what standard, because it changes how the reel has to be played.

Synchronization (sync) #

Sync is what keeps multiple machines locked so their tapes play as one continuous multitrack recording. ADAT machines use a dedicated 9-pin sync cable; DTRS machines use their own sync cable and ID system. This is why a three-tape ADAT set has to be transferred as a set — the tapes were recorded locked together and only line up when they are played back locked together, which is also why an incomplete set is such a problem.

SMPTE timecode #

SMPTE timecode is a clock signal — hours, minutes, seconds and frames — recorded onto one track of a tape so the tape can be locked to other machines, to a MIDI sequencer, or to picture. On analog multitrack it is longitudinal timecode (LTC), an audible buzzing tone that occupies a whole track, normally the highest-numbered one, with the track next to it often left empty as a guard track to stop it bleeding into the music. Recording it onto a reel is called striping the tape. If one track of your transferred multitrack is nothing but a harsh continuous buzz, that is almost certainly timecode and not damage — and it is worth keeping, because it is how the reel gets lined up with a video or with the rest of the session.

FSK #

FSK (frequency shift keying) is the cheaper, earlier way of syncing tape to a sequencer: a tone that alternates between two frequencies, one flip per clock pulse, recorded onto a spare track. It carries tempo but no position information, so the tape has to be played from the top every time; the later Smart FSK variant added song position so you could start mid-song. Plenty of 1980s 4- and 8-track cassette and reel sessions have an FSK track sitting alongside the music, and like timecode it sounds like noise but is the key to reuniting the tape with the sequencer data that went with it.

What you get back: files, resolution and splitting

Digitize (transfer) #

Digitizing, or transferring, is playing back a physical recording in real time and capturing it as digital audio files. For analog tape this involves a calibrated machine and an analog-to-digital converter; for digital tape formats such as ADAT, DAT and DTRS the data is already digital and is cloned across a digital connection with no conversion at all.

Sample rate and bit depth #

The sample rate is how many times per second the audio is measured (44.1 kHz is the CD standard, 48 kHz is standard for video), and the bit depth is how finely each measurement is stored (16-bit is CD, 24-bit is the professional production standard). For analog tape we recommend 24-bit at 44.1 or 48 kHz for most projects and can go to 96 or 192 kHz on request. Digital tapes are transferred at their native rate and depth. Full guide to choosing a sample rate and bit depth.

DAW #

A DAW (digital audio workstation) is the software used to record, edit and mix audio on a computer — Pro Tools, Logic, Cubase, Ableton Live, Reaper, GarageBand and others. Transferred multitrack files are delivered so they import into any DAW at a common start point. DAWs displaced the dedicated hard disk recorders that followed ADAT and DTRS, which is why material from that era now needs transferring twice over.

Session file #

A session file is the DAW document that stores the arrangement, edits, automation and mix settings, separately from the audio files it points at. Session files are format-specific and go obsolete faster than the audio does — recovering one from a legacy system is its own kind of conversion job, whether that means repairing an old Pro Tools session or reading the DDS tape it was archived to.

Track splitting #

Track splitting is cutting one long continuous transfer into separate files, one per song. A DAT of an album arrives as a single file; splitting it produces individual song files ready for streaming or download, and can be done from a cue sheet. Track splitting service.

Preservation master and access copy #

The preservation master is the flat, highest-resolution file that is never edited and is stored for the long term; access copies are the smaller, convenient versions — MP3s, references, CDs — made from it for listening and sharing. Keeping the two separate is the whole point of archiving: you only get one chance to play an aging tape well, and everything else can be regenerated from that capture. It is also why we archive at a minimum of 44.1 kHz / 16-bit and supply MP3s as an extra rather than as the deliverable.

Send us your tapes

Still not sure what you have? Start with what kind of tape do I have, or send us a photo. Analog reels: 2-inch 24 & 16-track, 1-inch 16-track, 1/2-inch 8 & 16-track, 1/4-inch. Digital tape: ADAT, DAT, DTRS / Tascam DA-88. Or contact us for a quote.


Contact us