The "Lemon" & "Cherry" effect.

[bobbletrox]

I'm not talking about fruit, folks!  I'm talking about an effect that was used on the song Lemon by U2 and Cherry by the Smashing Pumpkins.  The pedal must belong to Flood, because he produced both songs.  Billy Corgan discribes the effect as:

"warbly guitar courtesy of an effect that changes oscillation in ratio to signal input (the harder you hit it, the faster it goes)"

Basically, it sounds like a square wave tremolo whose rate changes speed according your picking dynamics.  It's a really interesting sounding effect if you happen to have those songs handy to listen.

This begs the questions: Has anyone heard of this thing before or know which pedal it is?  How hard would it be to rig the LFO of a tremolo so it changes speed according to picking dynamics?

[Mike Burgundy]

Wouldn't be very hard. The rough way would be to replace the speed pot with an opto, driven by an envelope detector.
Don't know about the specific pedal, but I'd say: build yer own!

[Paul Perry (Frostwave)]

in theory it is easy, as Mike Burgundy says. But in practice, there is a hell of a lot of tweaking, like with envelope follower filters, because if the decay rate on the envelope follower (which drives the LFO) is too slow, then the control voltage tends to ramp up & not vary enough, while if it is too fast to decay, then the reverse happens, and you lose the connection between loudness & LFO.
Would work best with generally fast LFOs, hence I assume the reference to "warbly", I don't know the song in question myself. I believe it is doable, but would take a bit of practice (with guitar playing dynamics) to get it useful & consistent. Personally, if you have a foot free, a LFO controlled by a rocker pedal would be better.

[cd]

I think it's on Moosapotamus's site, there's a schem for a resistive filter (Rattle Crow).  IIRC it uses an envelope detector to vary the resistance of a transistor in a feedback look.  This could be adapted (and I think LAL has an effect like this) to control the speed of an LFO.

[b_rogers]

maybe something like the Envelope Controlled Speed control on Dave Fox's Captain Coconut Provibe sectoin?

[Mark Hammer]

The new Line 6 Tap Tremolo does that.  Smack the strings and LFO rate pumps up, then settles back down to the default rate.  You can vary the envelope sensitivity.

The old E-H Polyphase also had envelope sensitivity on the LFO which produced a rate increase in response to higher amplitude signals.  Given that the Polyphase had a split output capability, that would permit it to do envelope-controlled vibrato.  It may well be the "magic pedal" you're looking for.

[R.G.]

Robert Penfold - "Dynamic Tremolo" in "electronic projects for guitar"

R.G. Keen - "Vibra Magic for EAN Tremolo", geofex.com