Stuart Memo has recreated the short-lived, stylus-operated Stylophone in HTML5, using Web Audio and his own vector-drawn keyboard library qwerty-hancock to demonstrate the basics of audio synthesis with the Web Audio API:
Article: http://tympanus.net/codrops/2013/06/10/web-audio-stylophone/ (via HTML5 Weekly)
...then see if you can spot the Stylophone featured in Bowie's Space Oddity!