Well our issue would be with the performance of that music, and the copyright and royalty required for the public to hear it. Which means once you have created your masterpiece, you want it heard while you fly.
This is definitely not an issue. Nothing different from what is done at any model day or freestyle comp where music is played on the field. It is just a matter of paying the licence fee to the collecting society. Easy and usually quite inexpensive. Here in the Czech Rep. it is handled by OSA
http://www.osa.cz, there is a variety of tariffs ranging from disco bars to telephone jingles, in our case the "performance at sporting event" applies although this may vary from country to country. What is more, besides the set fee there is usually a possibility to obtain a reduced fee for a non-paying event, a low spectators number (i.e. less than 1,000), etc.
In your country this is handled by the Performing Right Society
www.prs.co.uk, from what I heard last year a phone call may be enough to get all the details one needs. I know this is how the 3D Masters organizers did last year, they said that for a very modest fee they could play all the music they wanted all day long.
Of course this is irrelevant when you practice on your field without spectators.