Your friend needs to get hold of a copy of the Writers' and Artists' Yearbook. Most libraries stock it, as do larger branches of W H Smith, as well as other High Street bookshops. It's also available (at a discounted price) from Amazon:
http://www.amazon.co....qid=1265063103&sr=1-1
The Yearbook is packed with articles about getting published, together with listings of publishers and the types of work that they're interested in. It's the standard reference work for writers (and budding writers).
It's also worth visiting a really good bookshop and taking notes about which publishers handle similar works. If you live in or near London, the obvious choice has to be the world's greatest bookshop, Foyle's. (It's on Charing Cross Road).
Remember, as well, that others may have already sought out publishers for similar works (or have sought ways of distributing their own publications). It would make sense, for example, to ask a committee member of the Cinema Organ Society for advice. See here for details of how to email them:
http://www.cinema-org...OUT%20US/aboutus.html
The Theatre Organ Club might also be able to help:
http://www.theatreorganclub.co.uk/page6.htm
Chris