A music video is a short film, of variable length, that integrates a song or album with imagery that is produced for promotional or artistic purposes. Modern music videos are primarily made and used as a marketing device intended to promote the sale of music recordings. There are also cases where songs are used in tie-in marketing campaigns that allow them to become more than just a song. Tie-ins and merchandising can be used for toys or for food or other products. Although the origins of the music video date back to musical short films that first appeared in the 1920s, they again came into prominence in the 1980s when the channel MTV (originally "Music Television") based its format around the medium. Prior to the 1980s, these kinds of videos were described by various terms including "illustrated song," "filmed insert," "promotional (promo) film," "promotional clip," "promotional video," "song video," "song clip," or "film clip."