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54 QuadraSynth Reference Manual
Note that the waveforms in the QuadraSynth are different from those found in
samplers or many sample-playback units. Because the QuadraSynth has its own
filter module and amplitude module for each voice, the pure waveforms are
relatively bright--as bright as the original instrument can be--and have a constant
sustaining amplitude, like an organ. So if you listen to a piano voice without setting
the filter or amp to the correct settings, it won't decay after it is hit, as you might
expect. This gives you the freedom to create the timbre and dynamics you want,
instead of being chained to the parameters of the original sample.
Lowpass Filter
A filter varies a signal's harmonic content by progressively increasing attenuation
above a specified . The higher frequencies are filtered, while the lower frequencies
are allowed to Òpass-thru.Ó When the cutoff frequency is set high, the sound becomes
brighter; when set low, the sound becomes bassier since fewer harmonics are present.
Frequency Response Curve
Cutoff
Frequency
Filter
Amplitude
Frequency
00 99
The cutoff parameter changes the frequency at which the high-
frequency response starts to roll off. Lower values give a lower
cutoff frequency. A value of 00 will cut all sound off.
Static (non-changing) filter settings can be useful, but varying the filter cutoff
dynamically over time often produces more interesting effects. Modulating with
velocity produces brighter sounds with louder dynamics, which produces a more
accurate acoustic instrument simulation. Modulating with an envelope can create a
pre-defined change in harmonic structure, such as having a brighter attack and
bassier decay.
Each voice/filter combination is followed by an amplifier whose level can be
controlled by a variety of modulation sources. This allows for creating sounds with
percussive or slow attacks, particular types of decays, tremolo, etc.
Filter and amp settings can interact. If the filter cutoff is extremely low, then no
signal will get through, no matter how the amp is set. Similarly, setting the amp for a
short decay wonÕt let you hear any filtering set for a longer decay. This is because the
volume will reach zero before the filter decay finishes.