From GameBrew - a wiki dedicated to Video Game Homebrew.
SoundboardDS is similar to a DJ's soundboard that is used to create a beat. It was ranked 9th in the NEO Summer Coding Compo 2009, APP section.
Download and extract file.
Place ROM and SoundboardDS folder to the root directory of the card.
You can make your own beats and import custom sounds by converting .wavs into .raw files using programs like switch (8 bit, 11025 khz).
Press buttons to play the respective sound, i.e. Button 1 plays SoundByte1.raw in SoundboardDS folder.
A - Record your voice
B - Play the recording