of Microprocessors

MUSIC SYNTHESIS PRINCIPLES 21
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Fig. 1-5. Mechanical sine wave generator
amplitude of the vibrations gradually diminishes, the frequency remains the
same. The rate of amplitude decay is dependent mainly on the amount of
friction present. If the spring is held by a person rather than the ceiling, the
vibrational energy lost to friction may be replenished by careful, synchronized
movement of the spring.
The importance of the sine wave is obvious if one realizes that all
natural sounds come from mechanical vibration. The vibrating members in
all cases are actually tiny spring-mass systems. Pieces of metal, logs, and
even the air itself have a degree of springiness and mass. Striking these
objects or exciting them by other means creates the characteristic sine wave
vibration ofeither the entire object or portions of it. In most cases, more than
one spring-mass equivalent is vibrating simultaneously, so the resulting
sound is actually a combination of sine waves of different frequencies and
rates of decay.
Complex Wavefarms
At this point, we are now prepared to discuss the most interesting
parameter of all in repeating waveforms, namely the shape of the wave itself.
The shape of a waveform influences its timbre or tone quality. Obviously,
there is an infinite number of possible waveshapes (and only a few less
timbres). The only restriction is that a waveshape must be a single-valued
function, which essentially means that the horizontal progression from left to
right can never reverse.