Tone Matrix is a interactive 16X16 square grid, with 3 pentatonic (five note scales) octaves running top to bottom and 16 16th notes running left to right, with a rhythmic delay effect on it. Just click on the squares to place notes on the grid. Hold down your mouse to activate multiple squares. Space bar to start over.

Pretty much anything you do on it will sound nice.
Have fun: http://lab.andre-michelle.com/tonematrix

I found this on buzzfeed.

Simple sinewave synthesizer triggered by an ordinary 16step sequencer. Each triggereToneMatrix: create your own loops on a simplified synth.d step causes a force on the underlaying wave-map, which makes it more cute.

Based on the AudioTool engine thus no sources, I am sorry.