Clicking Relays

Relays?
Wikipedia says "A relay is an electrical switch that opens and closes under the control of another electrical circuit. In the original form, the switch is operated by an electromagnet to open or close one or many sets of contacts." As with almost everything, the original is what we want. The originals look something like…

The "originals" are interesting because the electromagnet opening/closing the switch actually makes an audible click. The solid state relays you'll see out and about are not electromechanical so they do not produce lovely clicks, but they are more reliable for actual switching purposes.

Fun Fact: The first computer bug was an actual bug caught in a relay.

Let's get clickin!
As with everything here, the circuit is actually pretty simple. Nothing is creative or obscure in the circuit either. It's just a textbook transistor example...

That is more or less exactly what I used (I found the image after I set everything up, recorded some clips, etc). The motor in the schematic is of course a relay (unless you want to activate motors!). The +Vmotor is the supply voltage required by the relay/motor/whatever. If you use a variable voltage to supply a relay, it will work as a volume control. Using any synth CV source (gates and triggers work best), or any output from a logic chip (circuits in the Nic Collins book or similar) should get you some usable output. In the clips, I am using a dual LFO patch back into itself to drive the transistor. This LFO puts out voltages between 0-5V.