At high volume levels, having the vibrato modulate the amplitude sounds a bit odd, even though that’s what actually happens with the voice. I may put in an option to use a simple curve to control the Loudness instead.
I’m also not sure that the amplitude and vibrato rate should always be driven by the same curve.
It might also be nice to be able to specify the Loudness peak relative to the right hand side instead of the left side. That way, the amplitude could continue to grow, even after the Frequency stabilizes.
Theoretically, Loudness and Frequency could both be independent of the Left ramp up, but I suspect that’s overkill.
I’ll have to experiment and see how well they work.