Rocker pedal drone concept!

[Paul Perry (Frostwave)]

A theremin enthusiast asked me to quantise the frequency..... fortunately, the oscillator is voltage controlled, so I think it will be possible to use a LED display driver with a number of pots to step through up to ten discrete voltages as the input varies. Which voltages could be set to correspond to some chord structure. And it occurs to me that one could use a foot pedal giving a varying control voltage to do this.
Maybe someone would find this useful as an alternative to an organ style bass floor keyboard?

[R.G.]

That could work OK. I can forsee some practical problems, though. It may be that these are trivial, or maybe they'll help you work through them ahead of time.

What's the drift of a tuning voltage done with a pot like? I always get apprehensive about any scheme that directly generates musical notes that's not very, very accurate and can drift. Might not be a problem with good pots though.

To get from one note to any other, you have to go through all the intervening notes, and presumably there's no way with the guitar setup to mute along the way. I also worry about the precision which one can bring to bear on a rocker, although that may just be my own lack of coordination speaking.

I've been thinking about doing a standard organ-style drone pedal. There's a PIC octave-tone generator that can generate a full octave of musical notes, crystal controlled by the PIC oscillator, naturally. One could run this thing to generate the tones, then just key the tones to a resistive mixer and spit it out. It generates a couple of octaves up from the bass, so you could even divide down and make stairstep sawtooth tones for better sound than a buzzy square wave.

If you did that, all you'd need to do with your voltage source is have the voltage source gate the sound onto the output. In a rocker setup though, it still leaves the intervening notes problem.

As I say, these may be trivial.

[Jaicen_solo]

R.G, that would be brilliant!
Chris wolstenholme from Muse used to use an organ foot pedal so he could play acoustic without sacrificing the bass. I think it's a brilliant idea, i'd build one for sure if it was possible to get fairly smooth sounds out of it.

[Tim Escobedo]

As R.G. points out, a rocker pedal has to sweep through the steps to get to the desired pitch. I can't think of a easy way to make a treadle that will both change frequency and allow for muting the notes. It might be kind of interesting to make a VCA for such a pedal that's driven by a envelope follower off the guitar (or whatever the instrument happens to be), so that the rocker pedal follows the rhythm of the musician's playing.

I'm curious about drift, too. However the SDIY guys do this sort of thing all the time, so I'm guessing the concept is at least doable.

[Paul Perry (Frostwave)]

Believe it or not, a 555 timer has better stability than a guitar string (subject to a good pot, caps etc). It doesn't vary with supply voltage, for one thing!
And, I hadn't intended the notes to be in frequency order. You could set it to give any order (depending on the pots associated with each step). This might make it more useable, as might a gate so it only sounds when the guitar is playing.