5.4
5.4.1 RELATIVE CHANNEL VOLUME
VARIATION
The independently programmable amplitude control for each chan-
nel allows up to 16 levels if using the processor controlled amplitude
mode (bit 4 of registers 10, 11 or 12=0). In the case of a
decaying or steady note, when a note is played or “fired”, a frequency
may be set up in the coarse and fine tune registers and then an
amplitude value placed in the respective register 10, 11 or 12. The
value which is placed to play the tune can be an independent
variable, allowing channels to play their respective melody lines with
varying force.
5.4.2 DECAY
The main difference between a “piano” sound and an “organ” sound
is the speed with which the note loses volume. If all of the notes can be
decayed at a uniform rate, the automatic envelope generator can be
set to produce a decaying waveform. Each of the three channels can
have the same decay constant but differing playing times tosimulate
the same instrument with differing note-strike times.
Sound
5.4.3 OTHER EFFECTS
The addition of variable noise to any or all of the channels can
produce modification effects such “breathing” with a wind instru-
ment. Or noise can be used alone to produce a drum rhythm. The fact
that the noise dominant frequencies are variable allows “synthesizer”
type effects with simple processor interaction.
Other pleasing effects include vibrato and tremolo, the cyclical
variation of the frequency and volume. Because an intelligent
microprocessor is controlling the effect, they can be all keyed to the
tune itself or to other external stimuli.
A
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