Tenor Peter Hofmann started his musical career as a rock singer, and switched to opera, showing enough talent to be one of Bayreuth’s busiest heldentenors during the late 1970s and 1980s and make 29 appearances at the Metropolitan Opera. He even looked like both Siegfried and the frontman in a heavy metal hair band.  When his voice began to show some strain in the late 1980s, he left opera and became the German-speaking world’s definitive Phantom of the Opera, bringing gravitas, electricity, and a strongly expressive voice to the title character in Andrew Lloyd-Webber’s cheesy musical. Margalit Fox has a detailed obituary at nytimes.com.