of Microprocessors

48 MUSICAL ApPLICATIONS OF MICROPROCESSORS
from each track has its own separate gain control so that the relative
contr,ibution of each track to the resulting whole can be controlled. A final
mixdown run is done in which the multiple sounds are combined and recorded
onto the rwo- or four-track (for stereo or quad) master tape, which represents
the final result. Commercial multitrack machines typically have 8, 16, or
even 24 separate tracks. Most modern recording studios depend heavily on
multitrack tape for most of their serious work.
Obviously, such a setup would allow a single performer to play all the
parts of a piece one at a time and then combine them. Synchronization with
previously recorded material is accomplished by temporarily using the section
of the recording head that is scanning a previously recorded track for
playback (at reduced fidelity) to the performer. Most complex music performed
on voltage-controlled synthesizers is played in separate parts and
combined with a multitrack tape machine.
By now it should be apparent that tape manipulation methods are very
powerful sound modification techniques. One drawback, however, is that
often a considerable amount ofwork is necessary, such as careful re-recording,
accurate cutting, and keeping track of scores of little pieces of tape. Thus,
experimentation is hampered somewhat by the possibility of wasted effort.
Application of computer technology, even microcomputers, is now tremendously
streamlining the process and even adding some new tricks.
Electronic Sound Modification
Over the years, quite a few "black boxes" and techniques have been
developed for directly modifying sound. Generally, these devices consist
entirely of electronic circuits. Rarely, however, a mechanical system does the
bulk of the work and transducers are used for getting audio signals in and
out. Such cases are frequently the subject of intensive research to find costeffective
electronic substitutes for the me-ehanical elements.
The uses for sound modifiers are varied but can be divided into two
rough groups. Obviously, such devices are of great utility in the electronic
music studio for adding complexity to basic electronic sounds that by themselves
may be lifeless. The other application is as instrumental sound modifiers
for rock bands and small combos. The devices for use by this group are
usually named by the apparent effect produced. Thus, we have "fuzz boxes,"
"wah-wah pedals," and "infinity sustains," Fortunately, the physical effects
of most of these can be easily explained in terms of the fundamental parameters
of sound.
Nonlinear Amplifiers
Modification of the spectrum of a sound is perhaps the most dramatic.
Spectrum modification devices range from simple distortion boxes to sophis-