signal driven LED

[onboard]

I ran a few searches on this and am still confused. My idea is for a momentary switched loop box to feed a delay pedal in order to play along with the lingering delay. I posted a switching schem for it in A/B/Y momentary quasi phrase sampler

It was suggested to me that a signal driven LED would be a cool thing to add. You know, the LED will be a visual of the signal coming from the delay pedal as it decays.

I remembered a similar? circuit block in the Dr. Quack/Nurse Quacky. Is this specific to the rest of the envelope filter circuit or can I do the same with the pedal's loop return jack feeding the inverting input of any dual opamp and drive my LED off the non-inverting input?

Another idea is a NeoVibe mod suggestion using an NPN tranny's base tied to the LFO (or other signal) with the emitter grounded and the LED/R limit between the collector and +9V.

Man, I ought to just get an EE text book...

[onboard]

I guess I'll start with the NPN as a switch idea...