of Microprocessors

738 MUSICAL ApPLICATIONS OF MICROPROCESSORS
function used to compute intermediate shapes. Direct spectral entry is
allowed on another page in a similar fashion. Here, 32 vertical grids are
shown, each representing four waveform memory segments. With the light
pen, up to 64 individual harmonic envelopes may be drawn with up to eight
displayed at once. The envelope of interest is shown with a thicket line. The
actual waveforms placed in memory are straight-line interpolations of the
display values over the fout segment intervals.
The "sound sampling" page is the most distinctive feature, however. An
8-bit A-to-D converter can sample from a microphone or high-level input
directly into the waveform memory of a separate "master voice module." The
sample rate may be varied over a wide range in order to fit the entire sound
into the 16K memory or to match the sound's pitch period to the 128-sample
segment size. Selectable low- and high-cut filters and an automatic trigger
threshold with adjustable pretrigger delay are available. After a sound is
captured, its overall amplitude envelope is displayed to allow level adjustment
to make full use of the limited 8-bit dynamic range. As with the othet
pages, the light pen is used to select options and control operation.
Although these and other sound definition/capture programs are
independent, they are linked together through disk files and retained
contents of the waveform memory. Thus, the waveform drawing page may be
used to view, and modify, a sampled sound waveform. The harmonic entry
page may be used to view the spectrum of a drawn or sampled waveform.
Another page is available for designating which segments of the waveform
memory are to be the attack, looped sustain, and decay. It can even rearrange
the segments or generate new segments that are combinations of other
segments, all under light pen control. An important feature is that the
keyboard is always active. As soon as a waveform is in memory, it can be
played, at any pitch, at any step along the editing process.
A keyboard page is available for assigning different regions of the
keyboard to different voices and assigning the eight available voices to stored
sounds in various groupings. Another "patch page" is used to designate
which synthesis parameters are controlled by the pedals, joystick, keyboard
velocity sense, etc., all graphically with the light pen. A sequencer page is
used to capture, edit, and merge keyboard sequences to build up to eight
musical parts. A music language (MCL, Music Composition Language) and
text editor are available to allow complex scores to be typed in and compiled
into the internal sequence format. In all, the Fairlight CMI is a very flexible
insttument that combines the best features of direct computer synthesis and
performance-oriented keyboard synthesizers.
Direct Computer Synthesis Practice
Although keyboard and toolbox commercial digital synthesizers have
essentially taken over the market for "working" instruments, there are still