[sdiy] simple and effective ADSR circuit using ICs

[synthplayer88 at spymac.com]

Hi guys,
I was wondering if anyone can recommand any ADSR circuit build with only ICs and
no transistors?

I know it's possible to use two 555 timers triggered by the inverted oscillator
signal to create an ADR envelope, the first attack setting can be varied through
the voltage divider at the input of the first 555 and the timing RC can be used
for dacay then the second 555 RC can be used for Release but what about sustain?

thoughts?