There is only one file type that uses the .M5P extension:
MachFive Preset File
An M5P file is a preset used by MachFive, a sampler for music production. It contains a preset, which is an instrument or effect used by MachFive as the main unit for creating compositions.
MachFive comes with presets included but you can also load presets into the program. You can use th presets to produce performances, which are stored in M5M files.
M5P presets that come with the application are located in the "Preset" folder. You may see the M5P file in this folder but you will most likely come across the file when receiving the file from another user or website to load into the program.
Updated: March 3, 2017