Here is another attempt to working with the experimental Audio API in Mozilla.
It’s a graphical equalizer with a configurable number of bands and frequency range.
There’s still quite a lot of work to be done, such as setting up correctly the bands per octave of each filter, add shelving filters at the extremes, better/nicer GUI and logarithmic frequency scale for the filter’s response visualization.
Of course you’ll need a recent build of Mozilla Firefox with the Audio API patch.
Update: embedded video that David Humphrey made.