Lunetta Noodles

synaesthesia

After spending some time in other forums on this site I learned that a noodle, in the context of synthesizers, refers to a patch that generates a tune without human interaction. No doubt, this can be done with Lunettas too. With the remainders of the 4049 DCO circuit on the breadboard, and also a simple VCF that I experimented with, I put together this circuit. It consists of two 4049 sawtooth oscillators that generate a low frequency for the tempo (upper part) and a high frequency for the tone (lower part). The nice thing with the 4049UBE oscillators is that they also generate a pulse. The pulse of the LFO sawtooth oscillator is used to momentarily enable two 4015 counters to count the pulses coming from the tone oscillator. The output of each counter then in turn changes the frequency of the oscillators using a control voltage generated by the connected resistor network. This results in a pseudo-random sequence of tones with varying lengths.

Because the pulse from the LFO was a bit too long, I ran it through R11+C1 to shorten it. The 4015 enable input seems tolerant enough to handle the spikes. With the R+C values in the schematic I haven't observed the circuit to get stuck in a sequence yet, although that is certainly possible. With longer enable pulses I observed that a few times.

In my first attempt I tried to use separate enable pulses with different length for each counter, but that didn't seem to be necessary. So a common enable pulse is used here. A reset button could be added to make sure that the two counter do not stay in sync. Also, the outputs from the counters could be swapped (even across counters) to make the sequence appear even more random.

I then ran the output of the tone oscillator through the VCF, just because it was still on the breadboard, and used the LFO sawtooth output as a control voltage for the VCF. The circuit works fine without the VCF, but it sounds so much better with it. Voila, a nice simple noodle soup with a bit of CMOS, linear CMOS and an op-amp. No breakthrough in synthesizer noodle science, but too good to be removed from the breadboard without sharing it before.

JumpNoodle.mp3

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