Conveniently we have 8 columns of buttons on the Neotrellis and only 7 music notes, so we've got an extra column. I've updated the code.py file in the repo to to make use of this extra row for selecting among the 4 available wave form types. The currently selected type will light up white. Press the other keys in the last column to change the notes played by the other buttons between the different wave form types.  I'm hoping to make a video to show off the new functionality soon.