Some old audio formats from Unix used msf extension, so it might be that some kind of MP3 conversion is possible. Some users are also looking for a way to convert .msf files from Sony recorders (for example PCM-D50 Sony recorder) to some more common format, because they think that these files contain audio - they do not. The actual recordings are saved in ATRAC format and the .msf file contains just some information for playback (found as MSGLIST.MSF).
Open MSF file Open MP3 file