Tone.js experiment, a FM synth with some basic controls for modulation index and harmonicity. Effects are distortion and ping pong delay. Drum loops made with Logic Pro X. Synth can be controlled by hovering over the buttons, or by using the keyboard. The c major scale can be played with keys ASDFJKL; (on an English keyboard), and synth percussion sounds with keys XCVBN.
Idea for the audio visualization from this D3 tutorial https://www.bignerdranch.com/blog/music-visualization-with-d3-js/.
Check out Tone.js https://tonejs.github.io/