Inspied by the BeatBearing project, Damien Kee built a musical sequencer using the Lego NXT system –

Each coloured ball represents a different note. As the colour sensor passes over the top, the note assigned is played. Different rhythms are capable by placing the balls in different places on the holder.

Bonus points for the circular design!

From the pages of MAKE:

The BeatBearing 
Volume 17, Page 122