Had a look at low_pass_filter.js hoping to see the source for the filter written out, apparently that stuff is all built into the web audio api. It has oscillators, it has Highpass, Bandpass, Lowshelf, Highshelf, Peaking, Notch, Allpass as well as Lowpass filters. It does compression, delay, waveshaping, wavetables, even convolution! I had no idea it was that high level! I wonder what the square wave sounds like? Mmmmmm... square waves...
Here's the list: https://dvcs.w3.org/hg/audio/raw-file/tip/webaudio/specifica...
Don't know how much of that spec is implemented, but with all that you should be able to make some pretty crazy noises. The google moog code looks very easy to hack as well.
Once someone samples some of those old SID chips and the like into those wavetables we're going to see an explosion of html5 games with awesome 8-bit sounds.