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If the pitch reaches the upper pitch limited then it automatically folds down
to the lowest pitch limit and vice versa. The pitch then continues to increase
or decrease at the same rate. This effect is called foldover or wrapround.
Changing the pitch up and down rapidly produces a vibrato effect. This can
be slowed down by increasing the step time. A slow change in pitch gives
a glissando effect. If you want the note to stay in tune make sure that the
upward change in say DRE section 1 is the same as the downward change
in DRE section 2. You could of course have more complicated pitch
patterns involving a third DRE section. Pitch changes are especially effec-
tive in percussive effects using the noise waveform.
A phasing effect used to great effect by synthesiser players is achieved by
sweeping the pulse width. The step time can be used to slow down or
speed up the effect. Both the pitch and the pulse width can be swept
together using the same DRE sections.
The repeat device can be either on or off. When off each DRE section will
only be active once. When on the whole sequence of DRE sections will be
repeated continuously until the end of note duration. DREs are not active
during the release phase. Only DRE sections which have non-zero step
lengths will be included in the sequence. Patterns consisting of 1, 2 or 3
frequency sections can be repeated. The initial pitch or pulse width value is
reset at the beginning of each cycle. If the volume reaches zero before the
sequence is completed then the repeat device will have no effect.
10
30
0
0
0
0
Pitch change with DRE active
upper
limit
section 1
no further change
lower
limit
Repeat ON