Machiyuta has released TiMidity for the PSP, heres some info i pull off the net:
TiMidity++ is a software synthesizer. It can play MIDI files by converting them into PCM waveform data; give it a MIDI data along with digital instrument data files, then it synthesizes them in real-time, and plays. It can not only play sounds, but also can save the generated waveforms into hard disks as various audio file formats. - http://timidity.sourceforge.net/#info -