The DS Music Interface (DSMI) is a collection of tools that will allow you to use one or more DS devices as wireless MIDI controllers. Using the touchpad on your DS, you can control a MIDI capable music instrument or MIDI-driven visualization software. Using DSMI, the DS can also receive MIDI events. This can be used to drive the built-in Gameboy sound generator, or as control input in your homebrew applications.
The Nintendo DS hardware offers a variety of possibilities for creating music as well as interacting with music. TheRain first had the idea of using the DS as a MIDI controller and created the DSMIDI, a DS cartridge that adds a standard MIDI port to the DS that can be used by homebrew DS software.
But since making a DSMIDI requires soldering skills and is rather dangerous, we came up with another idea: Using the DS as a wireless MIDI controller. The MIDI signals are sent to the computer via Wifi, and a server program forwards them to MIDI applications.
Later, support for natrium42’s, DSerial was added, enabling MIDI input and output via standard oldskool MIDI cables.
The project’s primary applications are a touchscreen-based keyboard and a 2d “Kaos” pad. These are built using the included libdsmi library, which you can use to add MIDI controller or MIDI client capabilities to your own homebrew DS apps.
Wireless and wired MIDI for the Nintendo DS – Link