webaudio brings some interesting possibilities to the table
http://emberbeats.gavinjoyce.com/
A synth with qwerty keyboard support - gotta disable vimium! http://www.keithwhor.com/music/
Many instruments - very responsive but no qwerty support https://tympanus.net/Development/MusicalInteractions/
A nice list of 10 http://www.hongkiat.com/blog/virtual-instrument-web-browser/
Programability https://github.com/surikov/webaudiofont drums piano
AND EVEN VISUALS