This video, via casperelectronics, takes a look at DIY synth building and building an oscillator from scratch. And controlling your synth with a watermelon:
Learn how to make a variety of simple but flexible oscillators (tone generators) using a breadboard and just a few inexpensive parts. This video has been created with newbies in mind, but should still offer some useful info and novel tricks for more experienced builders.
2:20 OMSynth mini lab intro
3:10 Electrical components and tools
4:30 The CD40106 hex schmitt trigger
5:37 Basic oscillator
7:30 How it works
11:00 Playing with resistance
12:45 Controlling oscillators with light, touch and DIY resistors
16:52 Syncing oscillators to make a stepped tone generator
19:50 LFOs and interconnecting oscillators.
26:40 Combining LFO and sync
26:49 Wrappin up.
28:05 Party jams
29:39 Shout outs
30:05 Sleepy cat