It's a shame the Web Audio API still hasn't been updated to allow glitch-free audio in emulators like this. Playback seems really smooth!

According to the author, it runs better with Firefox than Chrome.

You may also have to tweak the cycles/frameskip parameters, assuming it's possible with this version. The tweaks rely on modifiers + function keys combinations. I don't know if the browsers will pass them properly to JS.

It ran really well for me in Firefox 26 on Windows 8. I got great sound and no glitches while playing Major Stryker.

See also the Native Client port: http://naclbox.com/

I'd love to benchmark these two solutions.

Obligatory reference to Atwood's Law, etc. etc.