of Microprocessors

SOME REAL ApPLICATIONS 739
many unusual applications and research situarions for which they are
unsuited. Several of these, such as experiments in human perception,
development of new synthesis rechniques, and data compression algorithms,
were mentioned earlier in this chapter. Add to these experimental compositional
techniques and scores that simply do not lend themselves to "playing"
on a keyboard and one realizes that there is still a great need for direct
computer synthesis hardware and software. As would be expected, much of
this kind of work is done in a university setting, but there are also a number
of commercial studios and individual composers who make use of such
equipment.
Whereas a toolbox synthesizer increases flexibility by "deintegrating"
the usual keyboard synthesizer and making use of some standard compurer
graphics techniques, a direct computer synthesis system goes much further.
Firsr, there is the computer's operating system. Rather than being hidden
behind a limited function "shell" program, the full array of file maintenance
and other operating system commands are available. Although these commands
must usually be typed in a rigid format, their great flexibility often
allows otherwise repetitive tasks to be performed with just one command.
Programs are even more individualized and disjointed. The data files that
link them together can be defined by the user according to the application
rather than having to conform to a rigid standardized format. In essence,
there is total freedom-and the responsibility to use it productively.
The most significant feature of direct-synthesis systems is that writing
new synthesis and manipulation programs is the norm. Full documentation
of existing programs and data file formats are available to make the job
straightforward. Contrast this with commercial toolbox synthesizers that
make user programming difficult to impossible in order to protect proprietary
rights. In most cases, direct-synthesis programs rely on conventional
alphanumeric input rather than the nifty interactive graphics characteristic of
the Fairlight and others. One reason is that only 10-20% of the effort in
writing a typical interactive graphics program goes toward solving the
problem; the rest is in the graphics interaction routines. Thus, in research
situations, most programmers get by on the simplest user interface possible:
typed commands. Another reason is that graphics programming is generally
not "portable" among different computer types or even configurations. Thus,
one group using Digital Equipment (DEC) computers would have a tough
time sharing a well-done graphics program with another group using IBM
equipment.
Real.Time Direct Synthesis
One constant research objective is to design and build hardware that
can, in real time, perform the same synthesis and processing functions that a
generalized delayed-playback software package can. Two approaches have