I viewed this in Firefox and the Java console reported errors
=== Minim Error ===
=== Likely buffer underrun in AudioOutput.
which might explain why there is some jerkiness. Also you need a stop() method to release the audio resources used by the Minim library - see the examples that came with the library they all have this method.
By the way in Processing you might try Tools | Auto Format to tidy up your code will make it easier for you to see how your code is organized.
Nice applet just a couple of problems to solve.