[sdiy] Dealing with velocity sensitivity / scaling on envelopes

[Mattias Rickardsson]

On 1 September 2017 at 15:13, Oakley Sound <oakleysound at btinternet.com> wrote:
>
>> RTZ ADSRs have their place....
>
> In the bin. :-)

Not if you're designing polyphonic multitimbral voice-stealing
analogue synths! ;-)

This is a very tricky situation, and although I agree that the
envelope should model a capacitor charging/discharging - and that the
velocity factor should generally act as a multiplier on the resulting
envelope rather than changing the envelope internally - and that the
nasty clicks potentially introduced by RTZ can be hopelessly
problematic, I clearly see the need of RTZ if there is a risk that the
synth voice is doing something unknown and irrelevant before the note
that is to be played. Starting the envelope from random values will
ruin the sound to some extent, and this is what can happen if the
voice is used for different timbres and/or sent to different outputs
on consecutive notes.

Depending on your application, Tom, you might or might not need RTZ,
but even without RTZ the velocity scaling could give you nasty
clicks... so it's not easy! I'm even thinking that a zero-crossing
detector would be useful in order to minimize those clicks when
changing velocity, but that's perhaps the topic of another luxury
discussion. :-)

/mr