of Microprocessors

MUSIC SYNTHESIS SOFTWARE
681
CALL LEVEL 1 TONE
GENERATION ROUTINE
USING WAVBCB AND
AMP = EVTAMP.
!TABLE LOOKUP OF
ENVELOPE CURVE) ..
CFVAL
Fig. 18-16. Level 2 tone-control routine
count milliseconds during each phase. The next four parameters give the
duration for each phase. Two additional parameters give the sustain
amplitude relative to the peak amplitude of the attack (remember that the
ADSR shape overshoots the sustain level during attack) and the overall
amplitude of the entire event.
The remaining parameters are used to control waveform switching.
Four parameters give waveform table addresses for each of the four envelope
phases. Since sound control blocks must be created to generate sound, their
addresses are stored in the event control block. The cross-fade value increases
from 0 to 1.0 as the old waveform fades out and the new waveform fades in.
The rate offade is arbitrarily set to complete in one-quarter of the duration of
the current envelope segment. The cross-fade increment is computed at the
beginning of an envelope segment such that this is true.