Here’s what the letters mean:
e — envelope number (0-9)
a — attack rate (0-15)
d — decay rate (0-15)
s — sustain level (0-15)
r — release rate (0-15)
wf — waveform — 0 = triangle
1 = sawtooth
2 = pulse (square)
3 = noise
4 = ring modulation
pw — pulse width (0-4095)
Here are the definitions of the parameters not previously defined:
Envelope — The properties of a musical note specified by the
waveform and the attack, decay, sustain and release settings of
the note. For example, the envelope for a guitar note has a
different ADSR and waveform than a flute.
Waveform — The type of sound wave created by the
combination of accompanying musical harmonics of a tone. The
accompanying harmonic sound waves are multiples of, and are
based on the overall frequency of the tone. The qualities of the
tone generated by each waveform are recognizably different from
one another and are represented graphically in Figure 7-3.
Pulse Width — The length of time between notes, generated by
the pulse waveform.
Now you can realize the power of the ENVELOPE statement. It
controls most of the musical qualities of the notes being played
by the sound synthesizer. The Commodore 128 has 10
predefined envelopes for 10 different musical instruments, ln
using the predefined envelopes you do not have to specify the
ADSR parameters, waveform and pulse width settings—this is
already done for you. All you have to do is specify the envelope
number. The rest of the parameters are chosen automatically by
the Commodore 128. Here are the preselected envelopes for
different types of musical instruments:
7-14
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