I used Sensacells that are on a generous loan to me from Bob Stratton, who is one of the Sensacell team members. This piece was shown, most recently at The New York Maker Faire, where it won an Educator's Choice award, on Sept 21 and 22 2013 at the New York Hall of Science and before that on October 14th and 15th, 2012 at the Garner Arts Center in Garnerville, NY.
Sensacells come in two varieties, HSI and M-30s. These are HSIs which is the higher resolution. They are pricy, at list price this is $11,520 of cells comprising an 8'x2' wall made up of 4 2'x2' chicklets. Being divided into 4 chicklets would allow one to space out the 2' squares a few inches appart, rather than place each right next to each other as shown here. The alternative would be to mount the tiles onto a single 1/2" 4'x8' piece of plexiglass. Each HSI tile is less than 6" square and has 6x6 LEDs and 4x4 sensors. The M-30 (not shown here) is less than 12" square and has 4x4 sensors and LEDs.
I programmed this in Flash/AS3. Bob Stratton and the Sensacell team provided me with the base classes to handle the serial control heavy lifting, though the real heavy lifting is done with a piece of hardware, also provided by Bob, called a sensanode, which massages the serial and distributes the data stream between nodes, in this case 8 tiles per node.
Originally this had 9 sets of sound samples and four note image types. I began experimenting with synthesizing the sound using AS3 but I found that limiting and time consuming, and thinking I wanted to program a toy and not a synthesizer, I eventually sampled the sound from my old-school hardware synths. I am using a range of modalities from Dorian, to whole tones and even a blues scale. Currently it is boiled down to 3 sounds and 1 image type.