What I am using them for has to be in midi format.
Sorry, but neither QuickTime Player, GarageBand nor Logic can convert an audio file to MIDI. MIDI isn't audio, it's just a series of commands to the MIDI device on what note to play and other parameters. There have been a few third-party applications that purport to convert audio to MIDI, but their success rate is quite variable, depending primarily on the complexity of the audio (the more complex, the more difficult it is for the application to determine what notes are being played in what sequence, and hence more errors result). You might find
this web site and it's linked sites helpful.