Sites like Restore.Media or Online Converter specialize in fixing M4A files that were cut off (e.g., phone died during recording).
How to Recover Corrupted Audio Files
VLC Media Player can often play "broken" or unfinalized files that other players can't. Import as "Raw Data" in Audacity: Download Audacity . Go to File > Import > Raw Data . RecordTMP (32) m4a
Apps like GarageBand or Audacity may create .tmp or RecordTMP files while you are recording to ensure data isn't lost if the program closes unexpectedly. How to Access or Fix the File Sites like Restore
Many third-party voice memo or call recording apps use this naming convention for active recordings. RecordTMP (32) m4a