Background Music, commonly refers to instrumental background music.

BackGround Music --- the music from an anime soundtrack. Soundtrack CDs are popular merchandise items.

Short for "Background Music." This is the music played in the background of an anime. Unlike music in most Western animation, the BGM in anime can be very sophisticated and can stand alone on its artistic merits. Some of Japan's most talented composers, performers, and singers have created music for anime. Anime shows can also generate enormous numbers of soundtrack CDs, ranging in style from Pop, Rock, and Classical, to experimental noise and traditional Japanese folk music. Sailormoon alone generated some 28 music CDs.

see background music