W2E

The "W" on the left hand menu is the choice for it. Pressing the W key on the keyboard also does it. The secret, though, is to right click on the waveform at the top. Then choose one of the three display choices. The one on the right, the "Music Note" is perhaps the most useful. If you pick, say "E5," then your waveform will display the relative strength of the 5th E note on a piano keyboard. Whatever display you now see will be recreated in varying intensity in the interval you click down in the channel display. 

Different channels get different waveforms. You could make the "high" points of your display react to "high notes" and low points of your display react to low notes.

It is processor intensive to create and fill in the sequence but it can be a great effect.

Feel free to ask more questions - It was rather obscure to me at first.