The Fidelipac, commonly known as a "NAB cartridge" or simply "cart", is a magnetic tape sound recording format used for radio broadcasting for playback of material over the air including radio commercials, jingles, station identifications, and music as well as for indoor background music. Fidelipac is the official name of the industry standard audio tape cartridge.

Sound recording and reproduction is the electrical, mechanical, electronic, or digital inscription and re-creation of sound waves, such as spoken voice, singing, instrumental music, or sound effects. The two main classes of sound recording technology are analog recording and digital recording.