of Microprocessors

736 MUSICAL ApPLICATIONS OF MICROPROCESSORS
Fig. 19-11. Fairlight eMI "toolbox" synthesizer
on the synthesizer, the last step of combining musical lines may be done in
real time on the synthesizer or in srages using a multitrack tape recorder.
What is amazing (and gratifying) is that the entire process, which can result
in a truly impressive soundtrack, may be accomplished by a single person in
jusr a few weeks or months.
One example of whar is effectively a toolbox synthesizer is the Fairlight
CMI (Computer Musical Instrument), which was designed in Australia. This
instrument is very popular in the studio and has in fact been used to produce
countless film scores. The "terminal" part of the system, pictured in Fig.
19-11, consists of a movable 73-note music keyboard, an alphanumeric
keyboard, and a graphics display screen. The display is rather mundane with
a strictly black-and-white resolution of 256 X 512. Integrated into it,
however, is an extremely effective light pen with resolution to the pixel for
direct drawing of curves and pointing out displayed items. Except for the
display, all of the computer and synthesizer circuitry is housed in a separare
enclosure. Program and data storage is on 8-inch diskettes, and the two
drives are mounted in this enclosure as well. Two 6800 microprocessors are
used for the main control computer along with another in the music
keyboard. Both processors have access to all sysrem resources without mutual
interference by taking advantage of the 6800's 6502-like two-phase clock.
64K bytes of read/wrire memory plus 16K for the graphics display is also
present.
The synthesizer portion is also rather mundane but, as will be shown
later, is very effective in practical situations. The logic for each of the eight
voices is on a separate voice board. Each voice board has a 16K X 8 sample
memory driving an 8-bit waveform DAC followed by an 8-bit multiplying