LightMP3 is a MP3/OGG Vorbis/FLAC/Atrac3+ player designed to drain little energy from your battery. Can decode MP3 and ATRAC3+ via Media Engine with CPU set at 20Mhz, OGG Vorbis with CPU set at 50Mhz, MP3 via libMAD with CPU set at 70Mhz, FLAC with CPU set at 100Mhz. With battery at 100% and display set to minimum brightness it should last 9 hours.

With battery at 100% and display turned off (press START while playing a track) it should last more than 11 hours.