of Microprocessors

114 MUSICAL ApPLICATIONS OF MICROPROCESSORS
Minimum System
Figure 4-5 shows the minimum hardware complement necessary for
direct computer synthesis. Note, however, that the only device limiting the
quality and complexity of the sound is the DAC and audio tape recorder for
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Fig. 4-5. Minimum system for direct computer synthesis.
recording the results. Otherwise thefltll power of the technique is available on
this system. More elaborate setups can materially improve speed and convenience
of use but do not directly improve the sound itself.
The program entry and editing facility is probably the most crucial in
providing an easy to use system. Music of significant complexity requires
dozens and even up to hundreds of pages of typed sound specifications, music
notation adapted for computer use, and other instructions. The ability to
easily enter and edit this information is ofgreat importance. Perhaps the least
desirable medium for this task is the old punch-card and printer listing
approach. Use of a CRT terminal is probably the most desirable of all
standard computer input techniques. Dedicated and personal installations
may use any technique that is appropriate or affordable, although the CRT
terminal approach is still the most likely.
The computer itself is not really very important. If one of the "canned"
direct synthesis programs is to be used, the computer must be able to accept
the language it was written in and have sufficient memory to hold the
program. Speed is important, since it directly affects the running time of a
synthesis program. The computer also should have "automatic multiply and
divide," a feature that increases the effective speed of most synthesis programs
by a factor of five or more.
Storage of Samples
It is safe to say that any serious direct synthesis program computing
nontrivial music will not run in real time. This means that the 10,000 to
50,000 samples needed for each and every second of sound simply cannot be
computed as fast as they are used. Also, without a great deal of difficulty and
loss of efficiency, the rate that can be computed varies erratically according to