seeking permission to use music
I or we [band member(s)], as owners of copyright in the song x, grant a non-exclusive license to [your names] of the right to use song x in whole or part on the soundtrack of the short film entitled [xxxxx].This license includes the right to screen the film at film festivals and online, in perpetuity

[THIS MEANS FOREVER! – OTHERWISE THEY MIGHT GRANT YOU A LICENSE FOR A SET PERIOD OF SAY FIVE YEARS]. The film-makers warrant that they will include a credit for the song and band in the film’s end credits.

…. also you should promise to send them a copy of the film…

Bear in mind that the musician doesn’t necessarily own the rights. If they have signed a publishing deal with a record company for example then the record company needs to give permission. This should be stated on the cover of the CD if there is one. It is worthless getting the rights from someone who doesn’t have the legal right to give them to you.  We don’t have fair use in Australia