The SID file type is primarily associated with Commodore64 (C64). Note: audio/prs.sid is the official registered MIME type for this file type; audio/psid is the file type being considered for use by .SID files under BeOS. The file that starts with PSID is a PlaySID file while the RSID file is a RealSID file. The RSID format was designed to contain tunes that are not PlaySID compatible, but strictly require a real C64 environment to run.