What is a 4MP file
While 4MP might be categorized as an audio file, it does not contain actual audio data. Instead, they are database files, containing information used by the database manager 4-MP3. 4-MP3 allows users to store and organize collections of different sound and audio files. With the help of the 4MP file, the large collections of sounds can be searched and browsed a lot more efficiently.
Opening a 4MP file will not play any music or sounds. Instead, they contain a database full of references to different audio files supported and organized in 4-MP3 collections. The supported audio formats include WAV, MP3, and VQF.
Here's a small, but not exhaustive list of programs that can open 4MP documents: