Pepsiman has posted this news:

Iíve written an ALSA driver for the DS sound hardware, with some help from Parrot. This driver has been enabled in the builds with CF support, along with userspace applications:

vplay - plays WAVs.
vrec - records from the mic.
mp3play - plays MP3s.

Only 8bit playback is working at the moment, and recording is not implemented yet. Stereo support is implemented, but has not been tested.

More info --> http://www.dslinux.org/blogs/pepsiman/