There is only one file type that uses the .TMP extension:
Finale Temporary File
File created by Finale, a music notation program for instruments, vocals, and more; contains backup data for the document you're working on; acts similar to a cache file; exists only while you're working in Finale and deleted when the program is closed; cannot be opened manually.
NOTE: You cannot manually create a TMP file in Finale and you'll most likely never see one.
Updated: December 21, 2013