An mp_ file extension is related to the audio format used by mobile phones.
MP_ file extension - Mobile phone sound
What is mp_ file? How to open mp_ files?
File type specification:
The mp_ file extension is associated with mobile phones developed by Motorola, LG, Samsung, Sanyo and other producers.
The mp_ file contains sound from mobile phones.
Seems to be obsolete format.
This mp_ file type entry was marked as obsolete and no longer supported file format.
This type of file is no longer actively used and is most likely obsolete. This is typically the case for system files in old operating systems, file types from long discontinued software, or previous versions of certain file types (like documents, projects etc.) that were replaced in higher versions of their original programs.