Part of LGBT history — and singing it out

The San Francisco Gay Men’s Chorus is a serious institution. Its productions are grand, its history is deep, and its discography is long.

The rehearsals, though, are not quite so serious.

On a recent Monday evening, as the chorus practiced for its Pride weekend season finale, members joked and needled one another in whispers. Choir director Timothy Seelig would occasionally be stern (he has high expectations), but mostly he kept the mood light.

“Thank you for singing the next (line) so early,” he notes, his tone dry as the desert. “You’re usually a little late.”

All of this made it even more obvious when the quiet settled just as the chorus began to practice a song called “41.” The number, and the lyrics that follow, are taken from a July 3, 1981, New York Times article headlined “Rare cancer found in 41 homosexuals.” But any indication that “Unbreakable” — the wholly new musical the group plans to perform, composed by (and starring) Tony Award nominee Andrew Lippa — would stay in that somber place for

Mason Trinca / Special to The Chronicle The San Francisco Gay Men’s Chorus rehearses “Unbreakable,” a musical work that explores 120 years of the history of LGBT people, composed by and starring Andrew Lippa.