7. The method of claim 6 wherein first and second series of synchronous background sounds are provided, said first series of background sounds being associated with said first series of phrases, said first series of background sounds and first series of phrases comprising a first track pair, and said second series of background sounds being associated with said second series of phrases, said second series of background sounds and second series of phrases comprising a second track pair, each said first and second track pair being related and reproducible independently of the other track pair at selectively adjustable relative volumes, whereby emphasis may be placed on one said series of phrases without diminution of the volume of said background sounds heard by the listener.
6. A method of instruction, comprising the steps of: (a) providing recordings of at least first and second series of related phrases, the phrases within each said series being separated by intermediate sections, the phrases of each said series alternating with phrases of the other said series without overlapping; (b) providing continuous recorded background sounds which are substantively related to the subject matter of both series of phrases; and (c) simultaneously delivering to a listener reproductions of each said series of recorded phrases and said continuous background sounds, said background sounds being reproduced simultaneously with said phrases and during the intermediate sections between said phrases, whereby the subject matter of each series of phrases is associated by the listener with the background sounds and with the other series of phrases so as to enhance the listener's interest and the effectiveness of the teaching.