These incredible microtonal MIDI keyboards have 211 keys per octave (normal pianos have 12 keys per octave) and each key can be custom tuned!  From H-Pi Instruments:

The cool think about these keyboards is that the buttons are very sensitive and can be played with a delicate and light fingering technique.

I apologize for neglecting to post lately - I just simply have not been able to make the free time. Anyway, many different laser beam music systems exist. The concept is simple: Break the beam and the beam’s corresponding sound is played. Musical laser systems can vary widely from performance-grade monstrosities [...]

Music of the Spheres, Inc. is the “Stradivarius of wind chimes.” Handmade out of powder-coated, aluminum alloy tubing, the chimes range in size from the average garden chime to the extraordinary 14-footer. Their chimes can be ordered in a surprisingly large variety of familiar or “exotic” tunings and you can even create your [...]

For those of you who enjoy diagrams, here is a great diagram off the systems in a traditional Native American flute.

From the diagram:
“From the mouth, the airflow is slowed down in the SAC (slow air chamber), passes the exit hole, then the little channel of the flue, to hit the cutting edge. Then the [...]

nitro2k01 from Gameboy Genius has a theory:
The cupper and aluminum works as a battery, much like the lemon battery taught in physics class. However because of the Al2O3 surface on the aluminum, which is released in an opscillating manner, you get spikes of voltage. This is what creates the sound. Compare it to the bubbles [...]

ADACHI Tomomi, an accomplished musician and instrument inventor from Japan, invented this spectacle called the “tomoring.” Springs, bars, wires, and strings are mounted on an acrylic board to be joyfully plucked, bounced, pulled, flicked, scrubbed and otherwise manipulated in any way imaginable! This odd instrument is completely physical (not electronic) with only piezo [...]