Madwaves MP-5-US MadPlayer Create your own music and beats in a range of styles and genres with a 600-instrument sound bank Plays MP3, WMA, WAV, MIDI, KAR, possible future formats via firmware upgrades Plays for over 10 hours on 2 rechargeable NiMH AA batteries (included, with charger) Designed for portable use or for hookup with a home stereo Upgradeable to Mac compatibility through download; water-resistant plastic body