Archival audio repair

I have a mp4 file that needs to be cleaned up and slowed down. It was originally recorded on a cassette tape or a reel to reel tape in the late 60's early 70's. There is a recording of pilots in the office club singing some songs about their aircraft... One song the audio level is good and the second it sounds as if the singer backed up from the mic. I believe the tape was recorded at 16 fps and is playing vaster which it will need to be slowed down a bit. There is some feed back that is present and I would like the audio to be cleaned up if possible.