html5 audio 1 - html5.by
html5 audio 2 - softsynth.com
https://developers.google.com/web/updates/2012/09/Live-Web-Audio-Input-Enabled
https://webaudiodemos.appspot.com/pitchdetect/index.html

Hz: 220 440 880 1000 2000 5000 10000 15000 20000 Форма сигнала:
Тон:
Hz: