This is based on Chuck Johnson’s adaptation of a design from Nic Collins’ book “Handmade Electronic Music” for the realization of “Vespers” by Alvin Lucier. The circuit is built on paper inside of a small box.
The circuit is a square wave low frequency oscillator, which makes the speaker pop with a click sound more like a metronome than a sustained pitched sound.  

I power the whole box with a 9v battery and the knob on the side adjust the speed of the clicks. 

For the output I connected a ¼ inch jack with a switch to be able to use the small speaker built into the box, or connect a different kind of speaker. I use this feature to be able to play with different resonators and with the spatialization of the clicking sounds.