of Microprocessors

DIRECT COMPUTER SYNTHESIS METHODS 113
radio quality that is quite sufficient for experimentation. Rates as low as 8 ksls
to 10 ksls with 8 bits are suitable for demonstrations and telephone quality
but with the bass present.
A Typical Direct Computer
Synthesis Installation
Until recently, very few of the computer installations used for music
synthesis were used exclusively for that purpose. Most of them were just large
campus or corporate computer centers with the added equipment necessary
for digital-to-analog conversion and occasionally analog-to-digital conversion.
One property of classic direct synthesis is that only a small portion of
the expense and size of the equipment necessary is specialized for sound
generation; the rest is standard computer gear that would be present anyway.
Thus, in such cases in which the computer center already existed, the initial
investment in sound synthesis was small. However, as we shall see later, the
calculations necessary to produce the millions of samples needed for even a
short musical piece can eat up large blocks of computer time, which, on the
large machines, is priced by the second. Thus, as a practical matter, usage of
the installation was budget limited after all.
Today it is possible for a music or electrical engineering department to
have its own minicomputer installation with the hardware necessary for
direct computer synthesis. Furthermore, these smaIl, inexpensive computers
have as much if not more power than the large mainframes of a few years ago.
Although these systems are less convenient to program for sound synthesis,
they are much more convenient to use because the computer's resources are
not shared with hundreds of other users. Also, the cost of maintaining such a
facility is no longer directly related to the running time of ditect synthesis
programs. It is perfectly feasible to allow a program to run all night computing
another iteration of the 2-min finale to a 20-min piece.
Microcomputers and personal computers are also at the point where it is
practical to consider their use in small direct synthesis systems for the
purpose of experimentation and increasing flexibility. The power of these
machines is surprisingly good with newer models equaling the power of
minicomputers three or four years ago. Microcomputers are easily interfaced
with conventional synthesis equipment for computer control applications
such as automatic patching or sequencer use. With the proper peripheral
equipment, they can do as good a job of direct synthesis for unique or
otherwise impossible effects as more expensive systems although at a slower
speed. The personal computer user, however, has only himself to please, so
program running time is even less of a factor than with dedicated
minicomputer installations.