Commodore 128 - Making Music on the Commodore 128; The ENVELOPE Statement

Making Music on the Commodore 128
The ENVELOPE statement
The volume of a sound changes throughout the duration of the
note, from when you first hear it until it is no longer audible. These
volume qualities are referred to as Attack, Decay, Sustain and
Release (ADSR). Attack is the rate at which a musical note
reaches its peak volume. Decay is the rate at which a musical
note decreases from its peak volume to its midranged (sustain)
level.
Sustain is the level at which a musical note is played at its
midranged volume. Release is the rate at which a musical note
decreases from its sustain level to zero volume. The ENVELOPE
generator controls the ADSR parameters of sound. See Figure 7-
4 for a graphical representation of ADSR. The Commodore 128
can change each ADSR parameter to 16 different rates. This
gives you absolute flexibility over the envelope generator and the
resulting properties of the volume when the sound is originated.
Figure 7-4. ADSR Phases
One of the most powerful Commodore 128 sound statements—
the one that controls the ADSR and waveform—is the ENVELOPE
statement. The ENVELOPE statement sets the different controls
in the synthesizer chip which makes each sound unique. The
ENVELOPE gives you the power to manipulate the SID
synthesizer. With ENVELOPE, you can select particular ADSR
settings and choose a waveform for your own music and sound
effects. The format for the ENVELOPE statement is as follows:
ENVELOPE e[,a[,d[,s[,r[,wf[,Pw]]]]]]
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