Leonard Lehrman never met Marc Blitzstein. Lehrman was still in high school in 1964 when the composer of The Cradle Will Rock and the original translator of Threepenny Opera (alas, not the version now on Broadway) died.

But when Lehrman was a music student at Harvard, the Blitzstein estate was looking for someone to finish an opera called “Idiots First,” based on a story by Bernard Malamud. Other composers—including Leonard Bernstein, a friend and onetime protégé of Blitzstein, had already said no. So Lehrman took a look at the score. He’s been channeling Marc Blitzstein ever since: completing unfinished works, putting on a traveling Blitzstein cabaret, and coming out recently with the 650-page Marc Blitzstein: A Bio-Bibliography.