DSP Robotics Support

MichaelBenjamin wrote:useful ratios for FM modulation oscs are basically in 2 groups:

1. fixed
you can use any semitone with a finetune of +-0.5 cent, basically the whole continuuous spectrum
it stays always the same, regardless of carrier freq

2. relative
relative mode takes the user input (midi note, hz) and changes modulation frequency in basically 2 modes:
A. basic, overtone mode, add/sub a fixed ratio of X * carrier_freq_hz
B. advanced, musical mode, add sub a fixed amount of semitones, depending on your musical system and the carrier position in it

3. ?

Perhaps I should elaborate -

There is nothing mysterious or math-y about this. I've made several FM (phase modulation) synths and I haven't a clue what your post is about. FM operator ratios are simply frequency multiples - with a modulator-to-carrier ratio of 1:1, the modulator and carrier are the same frequency, ratio 2:1, modulator is twice the frequency (an octave higher) and so on. All whole-number ratios result in waveforms with harmonic ('in-tune') partials; in-between ratios (1.41, 3.14, etc.) result in waveforms with inharmonic ('out of tune') partials - good for bells, percussion, etc.

As to Fixed and Relative, again - ? With many FM synths, an operator can be put into a 'Fixed' mode which means merely that it's pitch no longer tracks the keyboard, and it's readout switches to frequency in Hz rather than a ratio; useful with a low frequency for adding the 'thud' of an electric piano sound, for instance. another use is placing a Fixed fr op in the middle of a three or more stack to produce a phasing or chorusing effect.

Downloaded, thanks