A very nice take on an electronic instrument!
Many of us here at SparkFun are musically inclined (you may remember a photoshoot featuring our very own Testing Guru Pete Lewis and his Rockbox). It turns out, many of our customers are also interested in fusing electronics and music in cool new ways. Check out this project from SparkFun customer Peter DeSimone.
What you see in the above photo is the Air Harp. The Air Harp is an instrument built using a single Maxbotix LV-EZ1 ultrasonic rangefinder which allows the musician to "strum" chords in the air like an acoustic autoharp. There are also four pushbuttons that select up to 15 chords in a given key. A fifth pushbotton allows automatic transposition into any key. Basically, with enough practice, you could play nearly any song on the Air Harp! Check out the video for some more info and to see the Air Harp in action.