I’ve quickly knocked up an example using the new FrequencyAnalyzer class written by Ben Stucki
Please have a play Test FrequencyAnalyzer
Use it as is in default mode if you like – to change the song while it’s running simply click the stage.
If you want you can pass variables via the url, something like this:
freq = 0 – 5.
band = 0.1 – 1.
song = 0 – 10.