Grant Gustin and Melissa Benoist will definitely lend their voices, but find out who else will join them

Who's singing in The Flash-Supergirl musical crossover?

Supergirl type TV Show network The CW genre Superhero Where to watch Close Streaming Options

We know who will be terrorizing the heroes of Supergirl and The Flash during the musical crossover, but now we know when!

The vast majority of the action will take place during The Flash‘s March 21 episode, with the musical kicking off at the end of Supergirl‘s March 20 hour, similar to the Invasion crossover.

As EW previously reported, the crossover villain will be the Music Meister, who has the power to control people through song. He was famously brought to life in the animated series Batman: The Brave and the Bold, where he was voiced by Neil Patrick Harris. Casting has not yet been announced.

The Flash hour of the crossover, titled “Duet,” will be directed by Dermott Downs, and will feature musical performances from Grant Gustin, Melissa Benoist, Jesse L. Martin, Victor Garber (who currently stars on Legends of Tomorrow), Carlos Valdes, Jeremy Jordan, and John Barrowman (the Arrow alum also stars on Legends). Supergirl‘s David Harewood and Chris Wood will also have non-singing guest star appearances.

Supergirl returns Monday, while The Flash returns Tuesday, both at 8 p.m. ET, on The CW.