Gt-,. { MULTITRACK RECORDING

TEACHER UNIT GUIDE NOTES

BACKGROUND INFORMATION The process of recording sound to magnetic tape dates all the way back to the 1920s and '30s. The earliest efforts used steel tape, but plastic-based media began to be available in the 1930s. History was made in 1948 when Capitol Records released a recording of two songs by Les Paul. The record was the first to be created with the process of multitrack recording. Working and recording in his home studio, he stacked eight individual tape recorders together and developed a way of synchronizing their playback. This allowed him to perform and record a number of individual parts, one at a time, while listening to the previously recorded tracks. Although Les Paul sold the design concept for the eight-track tape recorder in 1954, it was not until the late 1950s that manufacturers began to seriously develop and market multitrack recording decks. The advent of the analog multitrack tape recorder gave rise to the modern recording studio.

During the 1980s digital technology was introduced into the recording process which included digital tape recorders, signal processing and mixing. Today, the entire recording process can be accomplished in the digital domain. Even with the many advantages of digital recording, some musicians still prefer to record using analog recording decks, citing that it produces a "warmer" and "fatter" sound.

With technological advancement and lowered costs, multitrack home studios that can produce high quality recordings are now commonplace. The most economical approach is the analog multitrack cassette recorder. These portable four- and eight-track mini-studios record onto standard audio cassette tapes and also include a mixer with a variety of features for recording and mixdown. While fine for creating basic demos in a home or school environment, they lack the sonic quality of their digital counterparts.

Affordable digital multitrack recording came of age in 1991 with the introduction of the Alesis ADAT modular digital multitrack recorder. This eight-track, rack mountable recorder allowed the average musician and project studio to enter the world of digital recording for a fraction of the cost of other digital recorders. A number of recorders can be linked together to create 16, 24, 32 tracks or even greater as the need may be. While modular digital multitracks (MDM) are somewhat more expensive than the analog cassette multitracks, they provide CD­ quality fidelity and are still conSiderably less expensive than larger, professional studio recorders. I MAGNETIC TAPE RECORDING The recording tape used in a tape recorder consists of a mylar backing coated with a layer of iron oxide particles. This iron oxide coating is where the actual recording takes place. During the recording process, the particles are magnetized such that they are realigned into patterns that correspond to the waveform of input signal.

Tape Width There are several standard widths of magnetic tape used on different recording machines. Standard cassette tape is 1/811 wide. Reel-to-reel tape comes in a variety of widths: home stereo and profesSional mixdown decks use 1/4" tape, professional multitrack decks employ 1n and 2" tape for anywhere from 8 to 24 tracks of recording. Wider tape allows not for only more tracks to fit on the tape, but also greater track width and greater track separation. Greater track width results in a higher signal-to-noise ratio, since more magnetic surface is available to record each track. Greater track separation helps to avoid crosstalk between tracks, where signal from one track erroneously bleeds over to an adjacent track. The wider tape used in professional analog tape machines is quite expensive though: $150 or more for a single roll of 2" tape.

Digital tape decks do not require wider tape to improve signal-to-noise or to reduce crosstalk. Due to the nature of the digital recording process, the tape formats have very little noise and virtually no crosstalk between tracks. There are two tape formats used in the current lineup of modular digital multitrack recorders. Standard VHSvideo tapes are used in the Alesis ADAT deck and the Tascam DA series uses Hi-8mm format tapes.

Analog Tape Formats Analog tape decks are set up to record in a variety of ways. Typically, the tape format indicates two issues: the number of separate tracks that the tape machine can record and whether the recording is done unidirectionally or bidirectionally. In a bidirectional system, the tape can be flipped over and played in the other direction. This is the approach of all home stereo machines.

Fig. 7-1 Full-Track - records a single track across the entire width of tape in one directiononly~ = ­

Half-Track Stereo - records two tracks on the tape in a single direction for stereo reproduction. This format is generally used for mixdown decks.

Quarter-Track Stereo - Records two track stereo in one direction and two track stereo in the other direction when the tape is flipped over. Standard stereo cassette and reel-to-reel machines use this format. Multitrack Formats - Multitrack recording allows recording on numerous individual tracks - from 4 tracks on inexpensive personal recorders up to 48 tracks on large professional decks. Multitrack recording allows one musician to play and record all of the separate parts of a song. This process is called overdubbing. The person records the first track; and then, while listening to that first track, records another instrument or vocal line onto another track. This process can be repeated for as many tracks as the tape machine is capable of recording.

Even when recording a live ensemble, multitrack recording is important because each instrument or vocal part can be recorded on its own track. This allows more flexibility for creating proper balance between parts in the final mix. Also, if one musician makes a mistake, that part alone can be rerecorded without forcing the whole ensemble to redo the work.

Some tape recorders allow you to switch between different tape formats. For instance, most of the inexpensive portable cassette multitrack units allow you to switch between a quarter-track stereo format and 4-track unidirectional recording.

TAPE MACHINE CHARACTERISTICS Tape Heads The tape heads are the components in a tape recorder that carry out the magnetizing duties. In professional machines there are three different tape heads: 1. The erase head erases material that was previously recorded on a tape. 2. The record head records the new input signal onto the tape. 3. The playback head plays back the signal that has been recorded onto the tape. Many of the less expensive tape machines use only two tape heads. The record head and playback head are combined into one dual purpose head.

Digital tape recorders such as the Alesis AD AT use a rotary head similar to a video tape recorder, rather than the fixed heads that are used in standard analog tape machines.

Tape Speed Some tape machines allow for switchable tape speed. In analog recording, higher. tape speed settings create a better quality recording, but, of course, allow less material to be recorded on the same length of tape. Tape speed is usually measured in inches per second (ips). Standard cassettes run at 1-7/8 ips, while most multitrack cassette decks offer a double-speed option of 3-3/4 ips. Professional reel-to-reel machines allow for even faster speeds, typically 7-1/2 to 30 ips. Most multitrack and higher end stereo decks also feature variable pitch control which allows for fine adjustments to tape speed, thus changing the pitch and tempo as well. I TAPE MACHINE SPECIFICATIONS WOW and Flutter - As the tape travels past the tape heads in an analog deck, slight variations in speed or alignment can occur. These fluctuations, when audible, are called flutter. Also, the tape may become slightly stretched at times when passing the tape heads, which causes a slight variation in pitch of the sound. This is known as wow. Measurements of wow and flutter are used as standard specifications in rating analog tape decks- the lower the percentage of wow and flutter, the better it is (e.g., ±0.08%).

Wow and flutter can be a fairly annoying problem on analog cassette decks. They are much less prevalent in analog reel-to-reel decks because of the wider and heavier recording tape used. Wow and flutter are not an issue in digital recording.

Frequency Response - Frequency response is a measure of the range of frequencies that the tape machine is capable of reproducing. The specification is generally listed as two frequencies (lowest and highest reproducible frequencies) and an error tolerance level of plus or minus so many dB (e.g., 30-18,000 Hz at ±3dB). The wider the range and the smaller the error margin, the better. Analog cassette multitrack and stereo tape decks lack some of the high end frequency response of their digital counterparts. The frequency response of digital recorders is dependent upon their sampling rate. (See Unit 5.). The current generation of digital recording systems can produce a full frequency response range of 20-20,000 Hz with a near flat or even response tolerance.

Signal·to·Noise Ratio - The signal-to-noise ratio, or SIN, is a comparison between the level of desired signal and the amount of undesired noise present in a recording. It is often referred to as the noise floor and is measured in decibels; the higher the dB level, the better the signal-to-noise ratio will be (and thus, the lower the noise floor). On a spec sheet, it might be listed as follows: SIN = 75dB.

Cassette tape players are particularly prone to tape hiss which results in a poor signal-to-noise ratio (high noise floor). This is why virtually all cassette recorders include a noise reduction system (see below). The signal­ to-noise ratio for digital recording systems is dependent on the sampling '1esolution (the number of bits used for each sample-"see uniteS). With digital systems using 16-bit or greater resolution, the signal-to-noise ratio and dynamic range is very high. When recording, it is important to set the record levels of the system to their maximum gain without inducing distortion to obtain the best signal-to-noise ratio.

Bias and EQ - On most cassette tape decks there are three choices for tape bias and EQ: Normal Bias at 120~s EQ, High Bias at 70~ EQ (for Chromium Dioxide tape), and the Metal Bias at 70~s EQ. While it is beyond the scope

of this book to ex lain bias and EQ in de I it is im ortant to understand two things: 1) the switch on the tape machine should match the type of tape being used for the recording, and 2) High Bias and Metal tapes provide increased signal-to-noise ratios and greater frequency response. Bias and EQ settings do not apply for digital tape recording systems because they are not calibrated the same way.

NOISE REDUCTION One of the unwanted by-products of analog tape recording is noise or tape hiss. Therefore, most consumer tape decks and portable multitrack recorders include some form of noise reduction system. Professional studios that use analog recording generally employ separate devices dedicated to noise reduction. There are two approaches to noise reduction that are commonly used: Dolby (of which there are several subtypes, including Dolby A, Dolby B, Dolby C, and Dolby 5), and dbx. Dolby is most often found on consumer decks, and is common on pro level machines as well, while dbx is the approach used by some multitrack portables and professional studios. The mechanics of these noise reduction systems are beyond the scope of this book, but it is important to understand that when one of the noise reduction systems is used in recording, that same system must be used in playback. This has obvious implications for distribution of recordings, since not all decks employ the same approach to noise reduction.

Because of their much greater dynamic range, digital recorders do not require the noise reduction methods used in analog recorders.

RECORDING LEVELS When recording, it is important to set the tape recorder to the proper recording Fig.7 2' level If the recording level is set too high, the recording will be distorted. If it is set too low, the recording will have unnecessary noise. The goal is to record the signal as hot (high) as possible, without reaching distortion levels. The tape recorder is equipped with meters which display the strength of the signal over time. These meters might be in the form of a mechanical needle that jumps with the signal levels (called a VU Meter) or a series of LEOs that successively light up " or go out as the signal level changes.

. The maximum levels for recording to analogtapeaiffer from recording to a digital recorder. When recording to analog tape, the level should be set such that the average signal is around 0 on the meter (the cutoff point between green and red) with occasional jumps up into the red to about +3 or +5. For pieces with a wide dynamic range, the levels should be set so that the loudest passage can be recorded without distortion. One advantage of analog recording is the ability to record a signal that has occasional jumps above 0 on the meter without noticeable distortion in most cases.

Whf'n Tecordinll dillitallv, it is important not to exceed 0 on the record meter. As soon as it is exceeded, a very audible and harsh distortion occurs. Therefore, it is always best to make sure that the record level is set so that the loudest passage is a few decibels below 0 on the meter. Using a somewhat lower recording level when digitally recording is not typically a problem since the signal-to-noise level is better to begin with.

MULTITRACK RECORDING TERMS AND CONCEITS Overdubbing - This is the process of successively adding additional tracks to a recording without erasing the previously recorded material. During overdubbing, the musician listens to previously recorded tracks while recording the new track. With this process, a single musician could play and/or sing all the parts to a piece, one at a time. Musicians also use overdubbing to record multiple "takes" or versions of an instrumental solo or vocal track and then choose the best one for the final mix. (It is also common to choose the best sections out of a number of different takes and then "assemble" a final take.) fach additional take or overdub on a multitrack tape recorder requires the use of a separate track.

Track Synchronization - Without track synchronization, overdubbing would be impossible. After recording the first track, a musician needs to listen to Fig. 7 3 it while recording the second track. Since the record head and the playback head are located side by side, there is a time delay as each point on the tape passes from one head to the next. Because of this offset, what is recorded on the second track would not be in sync with the first track. In order to eliminate this problem, the record head on multitrack decks also serves as a playback head. This allows the user to monitor previously recorded tracks while recording a new one.

Bouncing Tracks - If a multitrack tape recorder does not provide enough separate tracks to record everything the musician would like, it is possible to use the process of bouncing tracks to extend the possible number of Fig. 7- 4 tracks available. When bouncing tracks, several previously recorded tracks are mixed together and rerecorded onto another empty track. For instance, if three tracks were already recorded on a four-track deck, these three could -.., be bounced to the fourth track, thus freeing up all three of the original tracks to record new material.

There are some problems with bouncing tracks. First, because the tracks that are bounced are mixed together into the new track, it is not possible to work with any of them independently from that point - they have become a new single track. Thus, when bouncing, one must be careful to achieve the right balance between the bounced tracks when they are mixed during bouncing. (This mix during track bouncing is called the submix.) A second problem with bouncing tracks when using analog recorders such as cassette multitracks, is that additional noise is added to the recording each time tracks are rerecorded onto a new track. This roblem is severe enou h that usually only one or two generations of bouncing are workable. Tracks can be bounced and submixed on digital systems without a noticeable increase in noise.

Punching In - When recording a track, a musician may make a mistake. Rather than rerecord the entire track, it is possible to rerecord only that section where the mistake was made. The recording is set to begin at a point somewhat before the error. The engineer then begins playing it back, and the musician begins performing the part again. When the phrase or

section that needs replacing is reached, the engineer IIpunches in" the record button. Then at the end of the phrase or section, the engineer "punches out." In this way, only the section which contained the error is replaced. With digitally controlled systems, precise punch in and punch out locations can be preset or programmed for automated punches during recording.

Mixing Down - Mixing down is the process in which the tracks of a multitrack recording are combined, balanced and rerecorded in a standard stereo format in preparation for duplication and final distribution. Common stereo recording devices for the mix-down process include analog reel-to-reel half track decks, DAT (Digital Audio Tape) decks, MiniDisc recorders, and direct-to-disk recording systems. A high quality stereo cassette recorder can also be used, but the final sonic quality will not be as good as the above-mentioned systems.

TAPELESS RECORDING All tape recorders, analog or digital, record and play audio information in a linear format; that is, sound is recorded across the length of the tape, one moment after another. The user must fast forward or rewind the tape to get to a specific location of a sound or song. With disk-based digital recording, however, recordings are in a nonlinear format. Referred to as tapeless or direct-to-disk recording, the digital audio information is stored on a hard disk, MiniDisc or Zip disk. A major advantage of this approach is random access- the capability to edit or play instantly from any point in a recording without having to fast forward or rewind to get there.

There are two approaches to tapeless recording: personal computer-based digital audio multitrack recording pl'Ograms.anddedicated hard disk recorders. Both approaches offer sophisticated recording, editing and mixing capabilities. Digital multitrack programs use the built-in hardware of the computer, and offer the advantages of easily updatable software and the computer monitor's large screen graphics. Most dedicated hard disk recorders have the advantage of a portable table top design and inclusion of a hardware mixer for a more direct user interface. The least expensive dedicated systems are the MiniDisc (MD) recorders which generally combine four-track recording with a simple analog mixer. At the high end are 16-track recorders complete with digital mixing, multi-effects and a host of other features. Tapeless recording has significant advantages over tape-based recording. Because of its non-linear format, powerful editing features allow an individual sound or an entire song to be broken down into parts and then played back in any order. This method of editing is called a cuelist or playlist because the final playback order is made by assigning a sequential list of the individual cues. In this way, multiple arrangements of a song or takes of a solo can be easily assembled without destroying any of the original audio information.

This points to another advantage of tapeless recording: non-destructive editing. Numerous takes of a solo or vocal can be recorded and then assembled into the "perfect" take without erasing any of the previous takes. The same applies to punching in and punching out: numerous retakes can be tried without erasing previous material. Full-track-records a single track Half-track stereo-records stereo across the entire width of tape in tracks in one direction only. one direction only.

Quarter-track stereo-records Multitrack-records several stereo tracks in both directions. tracks in one direction only. Tape is flipped over to play in the opposite direction.

Figure 7 -1. Different Tape Formats.

Signal is Overloaded. Maximum Optimum Recording Results in Clipping Headroom Level without & Distortion Distortion + ...t...... ~...... ~ ...... _.....

Poor Signal-to-Noise Ratio

Noise Floor

Time ....-­Track 1 - Drums

Time Delay Track 2 - Bass

Erase Record Playback

Figure 7 - 3a. Without Track Synchronization. Because it takes time for the tape to travel from the record head to the playback head, the newly recorded track is out of sync with the previously recorded track-there is an audible delay. In this example the drums have been recorded on Track 1. A time delay occurs when the musician listens to the drum track from the playback head while attempting to overdub the bass guitar on Track 2.

~- Track 1 - Drums

Track 2 - Bass

Erase Record Playback

Figure 7 - 3b. Track Synchronization. On multitrack decks the record head is capable of recording and playback at the same time. By listening to the drum track from the record head while overdubbing the bass part, the tracks will be Step 1: Piano, bass and drums are recorded on to tracks 1, 2 and 3.

Step 2: Tracks 1, 2 and 3 are mixed ---­ and bounced to track 4. tilt tt

Step 3: Track 4 is a submix of the previous tracks. Tracks 1,2 and 3 are then avattable to record vocals and the sax solo.

Pian-.·p 7 _.:1 Prot'p~~ of t'P('ot'dinv_ houncin~ a MULTITRACK RECORDING

ADDITIONAL RESOURCES

READING: Anatomy ofa Home Studio: How Everything Really Works, from Microphones to MIDI Scott Wilkinson, Steve Oppenheimer, Mark Isham Mix Bookshelf/ Mix Books. 1998.

Craig Anderton's Home Recording for Musicians Craig Anderton Music Sales Corp. 1996.

How to Set Up a Home Recording Studio David Mellor Cimino Publishing Group. 1996.

Modern Recording Techniques David Miles Huber & Robert A. Runstein Howard W. Sams & Company. 1995.

Multi-track Recording for Musicians Brent Hurtig GPI Publications; Alfred Publishing Co., Inc. 1988.

The Alesis Adat: The Evolution ofa Revolution George Peterson Hal Leonard Publishing Corporation. 1998.

The Audio Workstation Handbook (Music Technology Series) Francis Rumsey Focal Press. 1996.

INTERNET RESOURCES: Independent Music Site: Multitrack Recording ~~:/ / members.aol.com/DCmagnuson/multi/ __~TipS;tricks and information about multitrack recording.

The Recording Website pttp: / / recording.hostway.com/ This a great resource site for information about multitrack recording. The Tapele iUdio Computer Audio Magazine . ://nctweb.com/studio/ . site has information and equipment reviews regarding tapeless digital recording.

The Use '"Guide to Studio Recording ttp: / / www.ozemail.com.au/~opmnet/ guides.hhnl other great site with lots of tips about multitrack recording. MULTITRACK RECORDING

VOCABULARY LIST

analog multitrack cassette recorder bias and EQ bouncing tracks crosstalk cuelist (playlist) dbx dedicated hard disc recorder digital audio multitrack recording program direct-to-disc recording (tapeless recording) Dolby erase head frequency response full track half-track stereo linear format magnetic tape MiniDisc (MD) mixing down modular digital multitrack (MDM) recorder multitrack formats noise floor noise reduction non-destructive editing nonlinear format Multitrack Recording Vocabulary - page 2

pitch control playback head punching in quarter-track stereo random access record head recording level signal-to-noise ratio submix tape width track synchronization wow and flutter