I read a fantasy novel that was implied to be part of a series around 20 years ago (was part of my high school library, not certain how old it was then). I don't remember the title or author, or admittedly large portions of the plot (or maybe it was just a disjointed book), and would like to request help here.
These are the elements I remember:
A young teenager (in what I believe is regular old Earth) receives a list of instructions from a composer friend of his. By going through the composer's house and taking a convoluted path through the neighborhood, that starts changing on him as he goes, he arrives in another world entirely.
The path ends in a hostile garden or hedge maze that is tended/guarded by a woman in a veil.
The village he ends up in seems pretty repressed. Something about another guardian woman nearby related to the first, but not immediately hostile.
Desert or a wasteland nearby that contain monstrous or demonic children.
The protagonist eventually learns some ability to leave shadows or decoys behind by breaking off pieces of his emotions, or psyche. He ends up using this to cross the local wasteland.
Climbs a mountain and sees his own face as an adult in a snow vision, although he doesn't realize it until he finally returns home to Earth and sees himself in a mirror again.
Someone wants a "song of power" or words of power and traps our traveler for it. The original composer friend is somehow related to this, but what the traveler ends up writing under duress is a trap, and magically blows the villain's home up.
The Song of Power opened the gateway to the Realm of the Sidhe, allowing young Michael Perrin to slip through. Now Michael faces years of captivity and deadly struggles for the future of the Realm and of Earth--leading finally to a terrible confrontation on the streets of Los Angeles, with the soul of humanity at stake.
Weaving the power of music, poetry, and myth into a headlong narrative of nearly overwhelming intensity, Song of Earth and Power is one of the most original fantasy epics of our time, a vast tapestry of relentless suspense, terrible beauty, and brilliant imagination. Originally published years ago in two parts, it now returns in a new edition rewritten by the author and published in a single volume as he originally intended. Wrote Analog on its original appearance: "A delight....A vision of Faery that may owe a bit to a wish to do it right. Read it."