There is a great piece of work by a Finnish composer Toni Edelmann who composed a host of songs from the LotR to a Finnish theatre production of the book in 1989.
I've sent this
link already somewhere else in the 'Downs but let it be re-linked. It is my version of "The Song of Boromir". The melody is the same as in the original but the arrangement is mine as well as the performance (the original was in Finnish and performed by a then leading actor of Finninsh theatre Taneli Mäkelä). It's a crippled one with only three stanzas of slowly growing instrumentation and the chorus coming only after them (unlike in the original where it comes after every stanza) but it will give you an insight into what the song is like.
I do think this is the most beautiful version of that song I've ever heard. The other compositions in Edelmann's work are at best almost as good as this is - and some are pretty bad. Sadly the record is no longer for sale as the Tolkien estate denied the reprinting of the record into a CD-format already during the early 21st century (the movie guys had clearly already bought the rights at that time?).