Zokk wrote:
AngelRho wrote:
That frequency shift causes the output frequency to be highly unstable across they keyboard, so linear FM on analog synths is mostly useless. On digital synths, this problem is resolved by causing the modulator to vary the PHASE of the carrier, leaving the fundamental pitch-stable
Well, that actually solves a minor annoying problem for me. Good to know.
There is a theoretical workaround, though I haven't figured out how to implement it effectively. If you can find a way to adjust the scaling of both the mod and carrier across the keyboard, you can make it work. In actual practice, I have yet to get the scaling right.
On the Obie Matrix 1000, which is just the grandbaby of the Matrix 6 without programming but with 200 user presets and 800 permanent patches, there is a scaling feature called a "tracking generator" that will adjust the output of a mod source. Linear FM is possible by disabling Osc 1 (modulator) and using the filter as a carrier wave (by pushing resonance as high as it will go so that it self-oscillates). As of right now, I've only managed to get three octaves of pitch-stable linear FM, and it's mostly only useful in percussive or sequencer type sounds. It's also very useful for interesting attack transients as well as the usual sound effects.
You might like knowing this: There is an alternative to FM if you want to get those kinds of sounds on an analog synth. Let's say you're designing a classic DX7 EP. The trick is to get a mod harmonic coefficient in the neighborhood of the 14th partial. You'll have better success using hard osc sync pushing the master frequency to an inharmonic frequency somewhere between the third and fourth octave above the slave. Shape that with a lpf eg and you've got it. It won't sound identical to a DX7, but it's pretty close!
06 Apr 2012, 11:27 pm
