From the article: "I doubt anyone would argue that song composition is a lesser art or any less deserving of full royalties than other arts."

Note that this viewpoint isn't historical: http://law.bepress.com/villanovalwps/papers/art31/ Copyright wasn't originally granted even to sheet music, if I read the paper correctly. In the USA, musical recordings weren't covered by Federal copyright until 1972, but rather were covered under state copyright. Older music still is.

Copyright on music is indeed debateable, and has been as long as copyright has existed as a legal concept.