Yamaha SY55 Product Manual page 40

Each element also has a pitch envelope generator and two filter cutoff en-
velope generators that control the SY55's innovative digital filter system. The
block diagram below shows how the various operational blocks within each
element are interconnected.
Digital Filters
Each element has two digital filters. Filter 1 (FL1) is switchable for either
low-pass or high-pass response, while Filter 2 (FL2) is a low-pass type. Each
filter has its own 6-segment envelope generator so that a virtually unlimited
range of dynamic filtering patterns can be produced. See page 63 of the "REF-
ERENCE" section for details on the filter cutoff envelope generators. Filter
cutoff can also be controlled by the element's LFO (low-frequency oscillator).
Low-pass and high-pass filters can be combined to create a bandpass re-
sponse, or both filters can be set for low-pass operation — each with a rolloff
slope of 12-dB/octave — to produce a steep 24-dB/octave low-pass curve.
The filters also have a resonance parameter in the low-pass mode that allows
you to boost their cutoff-frequency peak — all the way into oscillation if you
like. The following graphs show the types of filter response that can be
achieved.
TUTORIALS
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