Let's Design and Build a (mostly) Digital Theremin!

Posted: 12/22/2017 11:25:47 PM
dewster

From: Northern NJ, USA

Joined: 2/17/2012

Video 04 - Pitch Quantization

Like the Theremini, the prototype has pitch quantization, though it is only chromatic. There are 8 levels, 0 (none) to 7 (steps):

And, as with the Theremini, pitch quantization has very limited uses.  I want real pitch correction!

Posted: 12/22/2017 11:29:26 PM
dewster

From: Northern NJ, USA

Joined: 2/17/2012

Video 05 - Tuner

I love my tuner, it uses PWM and is quite useful and responsive.  Here I'm showing the brightness control, and quantization which makes it more readable, as well as the inverse mode (which I thought would be the bee's knees, but I've since abandoned):

As I mentioned earlier, the octave number will be shrunk to a real 7-segment display, and a 4 LED volume bargraph will be added.

Literally everyone who has gone down this road in the past at least tried to put some kind of pitch indicator on their instruments, and it's easy to see why.  Even if you have an excellent ear the Theremin will put you out in the weeds.

Posted: 12/22/2017 11:44:40 PM
dewster

From: Northern NJ, USA

Joined: 2/17/2012

Video 06 - Mutated Sinewave NCO

A phase accumulator NCO feeds a polynomial sinewave generator, and the sinewave is flipped per quadrant and squared one or more times to produce a smooth waveform that doesn't alias too much considering the harmonics it generates.  Even and odd, or just odd harmonics are on tap:

Posted: 12/22/2017 11:45:09 PM
dewster

From: Northern NJ, USA

Joined: 2/17/2012

Video 07 - Noise Source & Filter

A white noise source feeds a state-variable filter.  The filter frequency can be constant or can track the pitch number.  There are controls for damping, and mode: high pass, band pass, low pass, notch, and bypass.  The filter can infinitely resonate if desired:

The modified Chamberlin topology is pretty incredible!

Posted: 12/22/2017 11:58:44 PM
dewster

From: Northern NJ, USA

Joined: 2/17/2012

Video 08 - Male Vocal

Here a bank of four bandpass filters with moderate Q, fed by the NCO set to produce maximum even and odd harmonics, gives us a fairly realistic male voice:

Two resonances for the throat / mouth & tongue, one for the nose, one for the face / throat emission.

Posted: 12/23/2017 12:05:16 AM
dewster

From: Northern NJ, USA

Joined: 2/17/2012

Video 09 - Female Vocal

Here is the same filter bank and NCO doing a passable female voice:

The glottal dynamic function clearly needs some work.

Posted: 12/23/2017 12:09:20 AM
dewster

From: Northern NJ, USA

Joined: 2/17/2012

Video 10 - Male Vocal Breath Noise

The filter bank with the previous male settings is fed with filtered noise instead of the NCO:

Kinda scary!

Posted: 12/23/2017 12:17:23 AM
dewster

From: Northern NJ, USA

Joined: 2/17/2012

Video 11 - Female Vocal Breath Noise

The filter bank with the previous female settings is fed with filtered noise instead of the NCO:

Kinda sexy!

Posted: 12/23/2017 12:23:07 AM
dewster

From: Northern NJ, USA

Joined: 2/17/2012

Video 12 - Female Vocal & Breath Noise

The filter bank with female settings fed with a mix of filtered noise and NCO:

The sharp intake is startlingly realistic!  I scare my wife (and myself) with it.  Weird how our brains are wired for scared.

Posted: 12/23/2017 4:57:30 PM
xtheremin8

From: züriCH

Joined: 3/15/2014

wow dewster, your tupperware-party is starting to sound and look interesting. congratulations. the noise video is amazing, that really impressed me. i learned from vcv-rack, a free open source modular eurorack synth sw, how much fun it is to work with filtes and noises. and the breath intakes are really close to real, maybe that's why we associate it with scary or lusty. maybe you created the first theremin that got x-rated. and shipped with a parental advisory sticker on it. just teasing.: "no ma' it's just the theremin.."

some question marks: that wobbly pitch on the second video at 0:05 and the in the third at 0:33..? that remembers me like the open-theremin sounds alike when i have a switched-wall wart around (in my case the one for the strymon big sky, if i turn it off, wobble is gone well, not really but a bit better.) quantisation is something i still can't get around with. i think it's the spacing between notes. the start/end point..thing. but i see benefits like to learn phrygian or other more exotic scales, that are not obvious to our western-chromatic tuned ear. or different tunings like the lucy scale for example. colundi everyone?  which scales have you in peto on your machine?  that leads me to another question i had and was always to afraid to ask: that led tuner. now in action it makes a bit more sense...i worked some years ago some days with a local synesthetic artist and she told me much about how that is different and such, to see tones in colours. so that strikes me every time i see rgb leds and the possibility to create almost every colour with. but i don't know if such a thing would be possible, to have a big led changing colour according to the played note.

a nice book: "push turn move" it's all about interface design in electronic music, if you like fat heavy prints,1.7KG, it's published by bjbooks in denmark. if i could i would beam it under your christmas tree right away. cheeriooohohohoho.

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