First of all for those who don’t know, the monome is a music controller which is used to generate sound effects, is has a lot of push buttons which have different color back lights to generate a visual effect to. DJ’s VJ’s use the commercial version, but there are also available DIY kits, open source open hardware designs, the most simple is to use the Arduino with the monome shield, but you can build your custom shield or entire system.
The basic functions are, use a large keyboard matrix, with back lit buttons and based on the sequence which the user pushes the keyboard generate a MIDI output which is interpreted by a mixer or synthethizer.
The sound and visual effects can be customized if you build your own monome, most of the parts can be bought from Sparkfun, including the pcb’s, although there are open source projects, the programming part is not for beginners and you need some external MIDI interpreter which can be expensive.
Monome with Arduino: [Link]