I do not know if I am allowed to post links, but google "A brief introduction to early WDW Music" and take the first link. They give you a VERY detailed explanation of how Jack Wagner constructed the magnetic tapes
There were different technologies depending on if the music needed to by synched. Ride music that was synched was on single loop 8-track like tapes. Background music like on main street and in the rides queue lines were on self-reversing tapes that played different tracks forward and backward. It's actually a very interesting article.