MP1 is the extension given to files that store compressed digital audio material. The sound is encoded using the MPEG-1 standard. This is a lossy compression that cuts a frequency band that is inaudible by the human ear. Audio sampling may be at frequencies 48; 44.1; 32; 24; 22.05; 16; 12; 11,025; 8 kHz. The bit resolution used for compression is 8 to 448 kbit / s.

The MP1 format uses the Layer I of the MPEG-1 standard. This is the most simplified method used, for example, when sending materials during a teleconference. MP1 has been superseded by the newer MP2 and MP3 formats.