Definition(en): The Portable Sound Format (PSF) is a sequencer sound file format for video game music, created by Neill Corlett. PSF files contain audio data and a sequence player. A file with the .psf or .psf1 extensions will usually be self-contained files holding both the audio library data and sequencing data. A .minipsf or .minipsf1 will hold just sequencing data, while a .psflib or .psf1lib will contain the audio library data so these must reside in the same directory where used.