These two circuits are among my favourites simply because they're so simple.

The whole idea behind a suboctave generator can be very simple; take an input waveform with a certain frequency and output the same waveform but with half the frequency, i.e. one octave down. If dealing with squarewaves the only thing needed is a logic counter/divider.

I used a 4040 CMOS counter and used the squarewave from my oscillator as clock input, every output of the counter will generate a waveform with a frequency that is the original frequency divided by a predefined number:

• Output 1 - f / 2 (one octave down)
• Output 2 - f / 3 (1.5 octaves down)
• Output 3 - f / 4 (2 octaves down)
• Etc...

The idea for this circuit is not mine, it's actually spread all over the internet and has been used in many synthesizers. This is a digital ringmodulator that is simply the XORed output of two oscillators, the input is apparently supposed to be two triangle waves for best result, i didn't have a clue and was happy with the result even though i used squarewaves!

I used a 4070 CMOS XOR gate and connected my oscillators, decoupled as they were, and it works fine!

A good thing about using the 40-series CMOS logic is that they don't need buffering and they run out of basically any voltage from 2-15v, capacitive coupling can be nice though.