The diatonic octave can be played, starting at the bottom, as W-A-S-D-up arrow-left arrow-down arrow-right arrow. These are all options on the back side of a Makey Makey Board,
By using the back of the Makey Makey board, you can use W-A-S-D-F-G in addition to the 4 directional arrows, space bar and click. This keyboard takes advantage of that. This keeps the functionality (by natalie) of being sable to assign the instrument of your choice.