Issues with B3 and software

Posted: 10/23/2009 5:14:53 PM

Joined: 10/23/2009


I recently got a B3 deluxe and I'm having some issues with interference.. it's usually on the high notes, like a second tone in the background, which doesn't bother me, but sometimes it clashes with the note I'm trying to play, makes it sound like it's jumping up to a 5th. Is this normal? are there ways to avoid it?

Being a programmer, I figure it should be easy to use software to take the output from the theremin, figure out the pitch, and use it to control a proper synth, or maybe send midi commands.. Before I start writing my own, is there any software that can do this already?

Posted: 10/24/2009 4:11:12 AM
Joe Max

From: Oakland, California

Joined: 1/2/2009

I have a B3 Deluxe and I've not had any problem as bad as you describe with it. You might be getting some RF interference from an outside source. Have you tried playing the B3 in other locations? Do you get the same problem?

Dan Burns recommended to me that if you're playing in an area where interference is a problem, try shortening the pitch antenna by half-inch increments and see if it improves. You'll have to re-tune the pitch knob to compensate, but there's plenty of range to shorten the antenna up to few inches and still get a "zero" setting.

Dan was very helpful when I had a technical problem with my first B3, so write him an e-mail and tell him what's happening. His e-mail is:

I can say that it doesn't seem normal to me. There is always a very tiny bit of "side tone" if one listens very closely, but nothing so extreme as to interfere with playing. I use an analog delay and analog chorus along with a touch of mixer reverb with my B3 and it covers a multitude of sins...

Good luck!
Posted: 10/24/2009 4:39:22 AM
Joe Max

From: Oakland, California

Joined: 1/2/2009

So far as pitch tracking software goes, the issue with theremins is the continuous nature of the pitch. MIDI is not well suited for non-equally tempered pitches, and most MIDI instruments, even software based, are designed to play chromatic scales. There is the pitch bend control, but the range is usually limited to an octave at most. (Usually much less than that.)

There is the Wavefront converter that claims to work around the problem, but it's pricey hardware box. I've never tried one.

The description of what the box does from the manufacturer:

"The pitch bend controller (1-48 semitones definable) is used in conjunction with RPN (54H) portamento control to follow the pitch of the theremin. Pitch is resolved down to +/-2.5 cents over eight octaves with 10 cents hysteresis (to reduce the amount of useless MIDI data transmitted from wobbly hand syndrome.)"

What would be [i]cool[/i] would be a pitch to CV converter interface for a computer, but that would involve an digital-to-analog output device of some kind.

Better yet, a specially designed soft-synth with integrated pitch tracking. The DSP engine would have to be designed especially to generate continuously changing pitch (like a theremin!) instead of an equally tempered scale. The challenge with digital solutions is generating an "analog"-like sweepable tone without any digital "steps" in the pitch. Even good synth engines like Reason can't track really wide, fast pitch wheel moves without some "stepping" of the pitch.

Pitch-to-CV converters have always been limited by the process of pitch sensing. In order to get a reliable pitch, the circuit (or software) has to "count wave crests" to determine the pitch. The absolute minimum number is three repeating wave cycles, equally spaced (two cycles can't be reliably called a "pitch") and the lower the pitch, the longer it takes. How well such a sensing system could track a [i]continuously varying[/i] pitch like a theremin's is problematic to say the least.

But the folks at Wavefront say they can do it, if you've got $500 bucks...
Posted: 10/24/2009 5:59:10 PM

From: Croxley Green, Hertfordshire, UK

Joined: 10/5/2005

You could have a look at Pure Data. (aka Pd)

Limitations aside, I'm curious to find out what a programmer can do with a midi stream from a theremin. Simple note mapping sounds a lot like running your finger up and down a keyboard.
Posted: 10/25/2009 11:09:18 AM
Joe Max

From: Oakland, California

Joined: 1/2/2009

@GordonC: [i]"Simple note mapping sounds a lot like running your finger up and down a keyboard."[/i]

Therein lies the problem. Directly pitch-to-midi conversion, even if it tracks successfully, would yield arpeggios, not glissandos. Obviously the Wavefront system used the portamento parameter to get around this somehow. But even that isn't a simple solution, since the portamento amount is time-fixed so it has to be set to move from note to note at a given rate, which, to imitate the gliding pitch of the theremin, would have to be adjusted "on the fly" to make sure that the portamento-ing synth note "arrives" at the target pitch when [i]you[/i] do. Theremin-to-midi just seems like such a huge can of worms to deal with I'm skeptical as to how well even the Wavefront hardware will manage it.

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