Paul is planning to use public domain music, reinterpreted for his film score and wants to know what rights and agreements he will need.
Paul wants to know: Does a film producer need copyright permission for a classical film music score, if the score is being reinterpreted by the producer's own composers and musicians. He also asks whether copyright law applies to any of this, the original classical piece, the new score, or what.
Well, let's take the last part first. Copyright law protects any original work of authorship for a period of time. Nowadays, works are protected for the life of the author plus 70 years. Under older copyright law, the time-frame(s) were much shorter. Right now, most works created prior to 1923 are in the public domain, and can be used without permission.
So, if you're using a Beethoven piece written in 1820, you don't need anybody's permission to use the COMPOSITION. But, if you're using an existing RECORDING of that piece, you most likely DO need permission from the record label.
If you're having a new recording made, and you've got a composer and musicians doing a new arrangement, or interpretation, or a mashup, then THAT is actually a new work, and you do need permission to use it.
What you really need is a “work made for hire” agreement with those folks… So you will own the copyright in the new work. If you don't have that in writing, THEY, not you will own it.
If you own the copyright, because you do have such a contract, then you're free to use it however you want, including making different interpretations. But, if you don't own it, then the opposite is true, and you'd need a license to do anything at all with the score… even exhibiting the film.
The same rule is true if you've got a composer creating an entirely new, original score. you need to have written contracts with the composer who does the score, and with the musicians who perform it.
Its easy, in the excitement of getting a new project off the ground, to leave this kind of thing to good faith… but copyright law can be tricky and this requirement that things be in writing is important… So take the time to get things done right. The good news is that this isn't a matter of reinventing the wheel, so an experienced entertainment lawyer can get you the contracts you need quickly and cost-effectively.