of Microprocessors

122 MUSICAL ApPLICATIONS OF MICROPROCESSORS
Statements within the NOTRAN language are placed in strict time
sequence from beginning to end. Program flow and music flow are identical
and linear from one statement to the next. Statements are of two basic types,
control and sound specification. Control statements make no sound and take
no time themselves but do influence events occurring after their appearance
up until another control statement of the same type redefines the control
function. Voice statements (which describe the timbre or "stops" of a
specified voice) and tempo statments (which determine the speed of playing)
are of this type.
Sound specification statements, on the other hand, do cause the generation
of sound and take time in a musical sense. A single note statement, for
example, may consist of many separate note specifications, each corresponding
to an individual note in the score and all starting simultaneously. Consecutive
notes each have their own note statements. Thus, notes in NO­
TRAN are specified in two dimensions: horizontally for different pitches at
the same time (harmony) and vertically for sequencing. A note specification
specifies a voice, a pitch, a duration, and an articulation (such as staccato).
Additional parameters describing the timbre of the specified voice are taken
from the last encountered corresponding voice statement. After a piece has
been coded in the NOTRAN language, the job is essentially over. The
complete specification of the sound is contained in the resulting string of
NOTRAN statements, and all that remains to be done is to run the program
and record the results.
As can be seen, NOTRAN is highly structured and very limited. This
does not mean, however, that enhancements would not be possible. For
example, a couple of years after it was first defined and implemented, percussion
sounds were added. A percussive voice definition statement type was
added and percussive note specifications were formulated. This feature was
added, however, in a manner completely consistent with the existing structure
of the system. With such a constraint, there are definite limits to
expanslOn.
Maximum Flexibility System
A second type of structured music system is similar but has as a goal
maximum usable flexibility. Even with such a goal it is still necessary to
make simplifications although not nearly as severe. The MUSIC V system,
for example, retains the concept of a note that is best described as an event. A
piece consists of a quantity of events, each starting at specified points in time
independent of their durations or other events. Another simplification is that
the system actually simulates an idealized, modular synthesizer similar in
concept to the voltage-controlled equipment described previously. For the
most part, sounds are generated by specifying the inputs and interconnections
of imaginary modules that themselves must be specified. In most cases,