The most memorable sections in “Losing Music” recount John Cotter’s daily struggles: the frustration of trying to hear his companions at a restaurant, fretting that he’ll destroy his hearing aids in sudden rain, trying to have sex while wearing them (“You just have to learn how to hold your head”). He’s lyrical about sounds we take for granted: wind rattling windows, old-fashioned radiators hissing to life, a cat drinking water. But he reserves his most passionate writing for music, “a world you can live inside. … When you’re young and you’re the hero of a movie, and the Heifetz you play in your car or the Velvet Underground you first try out sex to isn’t just background, it’s location and weather. You feel it on your skin.” On one of the blessed occasions when his hearing and tinnitus aren’t at their worst, he listens to a recording of a soprano. Her voice is “like someone set a candle on the floor and the smoke rose and curled. You don’t see the wind without it — the wind’s too light to see.” Writing that precise and moving helps us to grasp the full measure of the losses Cotter mourns.