I enjoyed discovering the pedalSHIELD - it was an inspiration for my own first steps in putting together an audio application on the DUE, which is
described on my blog
My system implements a variable band-pass filter, using Fast Convolution, running at 44.1 / 48 kHz.
Whilst it was built for an application in Amateur Radio, extension to use as a general audio effect is obvious. The filter framework will support any filter shape (although the filter design aspect is currently specific to the band-pass application).
Unfortunately, my code isn't open source at the moment - it is part of a larger project.
