DY b’michlas kvod toruschu…..
I dont hear any chiluk bet. a stipulation prior to the transaction to friends which is void . to unspoken terms during the transaction. Fact of the matter is all terms must be out spoken b’shas mechirah. They can expect you to read jackets and shmackets but halacha requires all terms to be mentioned during a transaction.
Imagine in talmudic times if someone would sell an ox and on the horn of the ox it would say that this ox is not sold but merely rented . do you think his unspoken tem will be acknowledged? I DOUBT IT. what the music companies can do is as follows. in the first hand the merchandise is transfered, ie. when aderet sells it to its disributors. That transaction assumingly is done through a contract anyways. at that point they can add to the contract that they are leasing it to the distrb. (with rights to sublease) . then all subsequent transactions will be merely rented. because like DY said earlier you cant sell what you dont own.