The Harmonic (pulse modulation) Filter

The harmonic filter is based on a sinc function

sin(pi w f)/(pi w f)

where f is the fundamental frequency of the note and where w is a parameter defined by the 'factor' dial (number 6). For example, the figure shows w=3. For this case, every third partial is set to zero and the others are scaled according to the red X's. In general, one of every w partials is set to zero and the intervening ones scaled according to the formula. The frequency axis in the figure is scaled so that "1" is the fundamental of the currently sounding note.



The behavior of the harmonic filter in the TransFormSynth is controlled by the middle row of dials.



The 'depth' dial (number 5) balances the sound between all filtered (=1) and no filtering (=0).

The 'balance' dial (number 7) controls how the high/low regions are balanced when the pulse mod filter is active.

The 'frequency offset' dial (number 8) shifts the blue curve (and hence the red X's) left or right by an amount specified in Hz.