Here is another Formant based poly synth. I wanted to work on the problem of using CV to modulate the cutoff frequency for multiple filters. The problem with that is when you adjust the attenuverter for cutoff frequency on filters it will not do the same for all the filters at the same time if they are separate. So any offset you put in to make a starting point for your cutoff gets attenuated when you adjust the attenuverter knob.

As I write this, I realize that my current version of this patch does attenuate the envelopes at all. You can change the offset of the cutoff using the TACT-1 faders though.

To allow for each envelope to start and stop on its own, I had to split the polyphonic envelope signal and later merge the addition of the offset and poly envelope signals.

So, while this patch can be used, it is still a work in progress.

And I decided to use a filter with a little more character than the Bogaudio filter, which I still like. The Bogaudio makes that offset of the cutoff easy with the V/Oct input. But I wanted something else. So the Neo came into play. But there is no bandpass option. I wondered about how to work around that limitation.

My solution was to use a second Neo and invert the signal and add the two filter signals (polyphonicaly) together. It works but not as good as some other patches. The easy way to visualize this is to take two low pass filter curves and have the second filter have a lower cutoff frequency than the first. You will get two curves where the attenuation of the second signal is parallel to the first. Now inverted the second curve and that subtracts the second from the first. When the two cutoffs are far enough away from each other, you should end up with a bandpass curve. At least that is how I imagined it.