The awesome thing about modular synths, which have a comb module (like ModulAir), is that you can put envelopes around them, before and after, if you will, and therefore still have total freedom about the transient it produces. Ordinarily you would hit it with a kind of impulse wave, something that has a tight enough envelope to just create "one waveform" when you play it. This one then goes into the comb and keeps swinging, depending on your decay and dampening settings of the comb filter. OH, remember Triple Cheese?! The whole synth was exclusively comb filters, really, with just some impulse and envelope features.
To get bowing type attacks or behaviors you can just hook a noise up as sound source/waveform input and play with its envelope. The noise will "energize" the comb, so to say...but it can be anything, not just a noise. Detuned waves can avoid exploding resonances and help produce amazing sounds as well!
Anyhow, the whole clue about such a filter is that you hook key tracking into its frequency. It then becomes much like a physical modeling concept.
In some ways my Lord of the Springs is related to that, but it doesn't work with "sampled" inputs. Instead it has literally springs that you stimulate, like pure resonance filters. It's related, because it also just holds on to what you put into it in an even more physical way.
The challenge with comb filters is really to design the right kind of input. You can put a single snap (like a pulse wave turned all the way to one side) into them and it will result in a very thing sound, because it has no real body like a sine wave, which would have the richest body.
It's amazing to experiment with all this, especially velocity controlled changes to the impulse part and dampening.
If you can have an lfo on the frequency of the comb, you can get the most beautiful vibrato, because it just does more to the sound than if you were to generate waveforms directly. Highly organic!
So, yeah, please, start playing with combs. It's ridiculously awesome! There are some "dangers", though, and it can get fickle...but it's worth the "risk", haha.
