by Greg Bear
Book 1 in Songs Of Earth and Power series (1984)
There is a song you dare not sing – a melody that you dare not play, a concerto that you dare not hear: It is called a Song of Power.
It is a gateway to another world – a gate that will lock behind you as you pass, barring you from the Earth forever. Resist at all cost.
For it is a world of great danger and great beauty – and it is not good to be human in the Realm of the Sidhe.
The main plot is about Michael Perrin, a sensible young man who wants to be a poet. He befriends a composer named Arno Waltiri, who it is said to have written The Infinity Concerto, a piece of music so unusual that it not only drove its listeners mad but it made also many of those who listened disappear.