A method of creating and delivering an on-demand audio asset for inclusion in a creative is described. The method includes the steps of accessing a central processing environment, requesting at least one recording of at least a portion of an audio transmission generated from a communication device, generating at least one audio asset, adding the audio asset to a pool of related assets stored in a vault connected to the central processing environment, selecting the generated audio asset and at least one other related asset from the pool of related assets to form a creative, then requesting delivery of the creative to another communication device, and finally delivering the creative to the other communication device. The method is performed in part by a creative composition engine, which is also described. The engine includes a central processing environment having a processor, a digital recorder and a digital asset storage vault.