Who does not love messing about building software synthesisers? I know I do and a basic component for these are oscillators.
Oscillators are used in all manner of things but it is the wobbly wobbly oscillations that can be used to produce a sound that are of most interest. Such things have been around since the late 1800s but today one can recreate their functions with computer software. Here is a simple example I made using the excellent Audulus app.