The role is to provide a 'hook' - something the viwer will associate with the product, even if subconciously, when the music is heard independently. The rapid and massive rise of use of music in adverts, begun way back when Levis used 'Heard It Through The Grapevine' is proof that this oassociation is both powerful and successful. Now, advert music can guarentee a hit an advance of release - witness 'Make Luv' which shot to the Number One position having been embedded in the national conciousness via a TV ad. for Lynx deoderant.