We have an airdate for the musical episodes of The CW’s “The Flash” and “Supergirl”: The tuneful crossover will begin at the end of the Mar. 20 episode of “Supergirl,” but the main vocal action will take place in the Mar. 21 episode of “The Flash.”

That episode, entitled “Duet,” will be directed by Dermott Downs and will feature singing performances from Grant Gustin, Melissa Benoist, Jesse L. Martin, Victor Garber, Carlos Valdes, Jeremy Jordan, and John Barrowman. David Harewood and Chris Wood will have non-singing guest appearances in the episode.



News of the musical episode broke last August. There’s no word yet if, as executive producer Greg Berlanti had previously indicated, the episodes will both feature one original song.

Leads Grant Gustin and Melissa Benoist both belted out various tunes on “Glee,” and the casts are also stacked with Broadway vets: Garber was part of the original casts of “Sweeney Todd” and “Assassins” and has four Tony nominations. Martin originated the role of Tom Collins in “Rent.” In addition to starring in musical series “Smash” and the film adaptation of musical “The Last Five Years,” Jordan nabbed a Tony nomination of his own for “Newsies.” Barrowman began his acting career on London’s West End in “Anything Goes,” and Valdes was in Broadway’s “Once.”