of Microprocessors

746 MUSICAL ApPLICATIONS OF MICROPROCESSORS
Figure 19-14B shows how several CARL system programs might be
connected together using the pipe facility and the command line a user
might type to effect this combination. SNDIN will read shortsams from the
sound file called DEADSOUND, convert them to floatsams, and then
output them through its standard output to a UNIX pipe. The vettical bar
immediately after the sound file name on the command line designates a pipe
connection to the following program name. FILTER in turn gets the name of
the coefficient file to use (BRIGHTCOEFFS) from the command line, filters
the floatsams from its standard input, and outputs the filtered result to its
standard output, which in turn is piped to the LPREV program. LPREV is a
reverberation program that reads reverberation parameters trom the command
line and reverberates samples passing from its standard input to
output. The D parameter specifies the ratio of reverberated to original sound,
and the G parameter specifies the reverberation time. Many other parameters
are available, which take on default values when not specified. The results of
LPREV are finally piped to SNDOUT, which converts floatsams back to
shortsams and writes them onto a new sound file called LIVESOUND. Since
UNIX is a time-sharing operating system, all four of these programs are
actually loaded and run simultaneously. Thus, the pipes are actual in-memory
communication channels rather than temporary files as would be required in
other operating systems. Much more complex interconnection patterns with
parallel signal paths are also possible using special "branch" and "merge"
programs.
C-MUSIC is the heart of the CARL system for synthesis applications.
This program reads text from a score file and produces floatsams on its
standard ourput for piping to other programs or writing into a sound file.
The score file (or standard input if no file is specified) may have been prepared
by the user with a text editor or may be the output from a macroexpander or
high-level composition program. The brief discussion that follows should
convey the flavor of C-MUSIC, which is also generally applicable to MUSIC­
V, MUSIC-ll, and other family members.
A C-MUSIC score consists ofstatements, each ofwhich is terminated by a
semicolon. Text enclosed in curly brackets (n) may be placed anywhere as
comments. Score statements are grouped into four overall sections as follows:
1. Options
2. Instrument definitions
3. Function (table) generation
4. Notelist
The options section contains statements that specify several global
attributes applicable to the current "run" of C-MUSIC. These include the
sample rate, number of sound output channels (one to four), the sizes of
internal buffers, the random-number generator initial seed, and the default
function length. The latter is the size of waveform and envelope shape tables