A few Lunetta circuits I've been messing around with

[gasboss775]

This one can be made from 1/4 of a 4093 or 74hc132. It is an oscillator or a nand gate depending on the switch position.

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NAND Gate or oscillator.jpg
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[gasboss775]

Another Schmitt gate based oscillator, this one with a sync input as well as the gate input. The value of C1 depends on that of C2, will need to experiment more to see what is best as I don't know how to calculate it on paper. Q1 can be a bs170 or a 2n7000.

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Schmitt Oscillator With Sync input.jpg
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[gasboss775]

I have found the following oscillator with sync to work better than the one with the mosfet.

Note that with these simple circuits if the syncing oscillator runs at a higher frequency than the main oscillator that the oscillator will stall as the capacitor can't recharge quickly enough to sustain oscillation.

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share.jpg
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[gasboss775]

The next Schmitt oscillator isn't really a VCO as such however it does permit a degree of modulation of both frequency and pulse width which is very much dependent on the setting of the main tuning control VR2 as well as that of the actual modulation depth control VR1.

With VR1 fully clockwise and VR2 at maximum resistance it is possible to get around an entire octave of frequency modulation, however with VR2 at minimum resistance the maximum frequency modulation is equivalent to about a major 3RD going by ear.
The CV input was at VDD which in the experiment was equal to 10.04 Volts.

The relationship is frequency to CV is neither linear or 1V per octave but given its simplicity and that this is the Lunetta forum I think that is OK!

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Schmitt oscillator with modulation input.jpg
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[gasboss775]

This one is a square noise generator, basically it outputs random 1s & 0s. This can be fed into shift registers to produce random gates or random voltages ( using a DAC such as an R2R network )

The low pass output is just more slowly changing, effectively it gives an alternative random output.

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square noise generator.jpg
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[gasboss775]

This is a 3 bit DAC, has only been tried on the simulator but should work. With a hex inverter and a dual opamp you could make a Dual 3 bit DAC module, or with 2 hex inverters and a quad opamp you could make 4 3 bit DAC's.

The output is 0 to +10V, the inverters should be powered with a regulated +5 volt supply. The opamp (s) the usual +/- 12 or +/- 15 V supplies.

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3 bit DAC 10 V version.jpg
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[gasboss775]

A very simple VCO using a Schmitt trigger oscillator controlled by a Vactrol. Note this VCO isn't linear OR 1V per octave! Is very simple though, good for Lunettas!

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Simple Vactrol VCO.jpg
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[PHOBoS]

nice little circuits

I like how you used the same resistors in the DAC to get different values. You can leave out the 2.2M though,
the tolerance of the 4k7 is much higher than what it changes in total value. Also instead of using the 3.33V reference
for the non-inverting input of the opamp I think you can just attach it to GND and add an offset voltage to the inverting
input.

And yes, vactrols work great for those oscillators, the slight slew is actually great for percussive sounds.

[gasboss775]

[PHOBoS]

You mentioned "The opamp (s) the usual +/- 12 or +/- 15 V supplies." but you're correct that it wouldn't work with a single supply.