Filter interface bugs

[ebeling]

How can you have less than "no echo" ? Isn't that like having less than no oranges?

Well, echoes are not oranges in my opinion. A negative gain still produces an echo, it's just that every other cycle of the echo the waveform is flipped upside down. The problem may be that the parameter has a misleading name, which may be why you can sometimes see a polarity switch on echo or comb filter effects. But I would prefer just one gain parameter with values -1 < gain < 1 as I've said before. Setting gain to 0 would be the only way to have no echo at all.

[steve]

the echo the waveform is flipped upside down

OK. That's reasonable, though I agree that the terminology is problematic / misleading.

There is a way that you can achieve that with the current version of Audacity - not as simple as just setting a negative slider value, but the same result:

1. Duplicate the track twice so that you have 3 identical tracks
2. Apply "Echo" and "Invert" to ONE of the tracks
3. Select all 3 tracks and mix.

[ebeling]

Indeed, that's a very convoluted way of doing it. Besides, you also need to set the delay time in the inverted track to twice as long as in the other tracks, and I think the decay amount would need to be half as much.

No big deal, I resort to Csound for this kind of thing.

[steve]

you also need to set the delay time in the inverted track to twice as long as in the other tracks

No you don't. Try reading my description again.

and I think the decay amount would need to be half as much.

No it won't.

I resort to Csound for this kind of thing

If you are familiar with Csound, then that's probably going to be easiest for you.
If you want to become familiar with some of Audacity's more advanced features, you could do it with "Nyquist" (see: https://manual.audacityteam.org/man/nyquist.html)

[ebeling]

1. Duplicate the track twice so that you have 3 identical tracks
2. Apply "Echo" and "Invert" to ONE of the tracks
3. Select all 3 tracks and mix.

I tried it, applying echo to just one track, but what happens is that you get one instance of the original signal followed by echoes that are all inverted. That is not what I described.

This idea of mixing and inverting signals to simulate negative feedback is deceptively simple. Using only positive feedback g in the equation y[n] = x[n] + gy[n-D] I see no other way than to set the echo to 2D in one track and adjust the decay parameter to the correct amount (I realised I got the latter part wrong after some back of an envelope doodling).

And yes, I'm aware of Nyquist and like the idea of extensibility, but for me C++ is the language of choice for audio programming.