audio-only is a common term for the audio portion of soundtracks to video-based programs which exists without the footage.
The Nunica Internet Social Alliance and audio-only mediaEdit
The Nunica Internet Social Alliance deals with audio-only applications of music entertainment in an effort to keep it free. For instance, Nisa subsidiary NunicaMusicChannel has YouTube "videos", but in general they are audio-only in the general sense of marketing. Sometimes custom video footage is used as a "placeholder" music video as an effort to keep the account out of legal trouble, seeing as music video footage has been a subject of copyright filtering.