From the original SynthMaker forum (2004–2014), with its members’ names and dates.
GhostAddicts ·
is there a way to filter out harmonics seperately. Say i want the 2nd harmoninc to play but dont want the 3rd harmonic to play, is there a way to make a filter (i think band comb does this) to filter out specific bands of frequencys and could that filter then be adjusted by the note being played? kind of like additive synthesis coming from a subtractive synth.
infuzion ·
I would try notch filter(s). Do in Poly if for a VSTi!
GhostAddicts ·
isnt notch a filter that negates a certain freq? i think i would need parallel bandpass filters to create a bandcomb. but i was hoping there would be a way to put it in one block of code(admitedly i cant figure out filter codes for the life of me) but i also havent been able to control a filters cuttoff by the incoming frequency... and i do know its possible.
bootsy ·
by which method to you create the harmonics?
trogluddite ·
GhostAddicts wrote: control a filters cuttoff by the incoming frequency... and i do know its possible.
Most of the filter codes you'll find on the forum use the same 'normalised' (0 to 1) frequency range as the oscillators - although a few use frequency in Hertz. So if you feed the freq input of a (poly) filter straight from the note frequency of the MIDI-to-Poly it will exactly match the fundamental of the note. To set the frequency to the Nth harmonic, just multiply the frequency by N. As long as you always multiply the frequency by the same amount for every note, the filter should track the keyboard perfectly, so that exactly the same range of harmonics gets through no matter what note you play.
Polyphonic notch filters would allow the ultimate control over each and every harmonic - but you might need a lot of them, and they would need a very steep roll-off to work well for the higher harmonics.
The notches in a comb filter are spaced just like a harmonic series, which means that you couldn't select just one harmonic to be filtered out - always a series of them (say, every even harmonic, or every third one). For a very quick idea of how this might sound, play two oscillators together, but offset the phase of one of them (fixed difference, not modulated) - this is equivalent to a basic comb filter with keyboard tracking.
One other tip - If you decide to look for notch filters, make sure to choose ones where the filter co-efficient maths is hopped - otherwise you may end up using far more CPU than the oscillators of an additive design. Usually people mention in their posts when they use hopping, but if not, look for the 'hop' command (in Code) or 'jnz' command (Assembly) near the beginning of the code.
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