Syntho is a monophonic synthesizer inspired by the Korg Volca Bass. It features 3 oscillators with sine, saw, triangle, and square wave shapes over 6 octaves. Each oscillator can be detuned independently, giving nice/horrible pulsing as the oscillators go in and out of phase.
A low pass filter with resonance affects the sound of the oscillators. The filter self oscillates if you push the resonance way up.
There is a low frequency oscillator that can be set to affect the pitch of the sound generating oscillators, or the filter cutoff point. The LFO supports triangle and square waveshapes.
Finally, there is an ADSR envelope generator. The ADSR can be set to control the amplitude of the sound, or the filter cutoff point, or both.
The inner workings of Syntho and web-audio will probably be the subject of another series of video tutorials. But for now, the code is on GitHub.