Supergirl cast David Harewood and Chris Wood will also appear in non-singing roles, while original songs have been provided by both Crazy Ex-Girlfriend star Rachel Bloom, and the Golden Globe-winning La La Land lyricists Benj Pasek and Justin Paul.
You can get a good sense of the whole cast’s musical prowess here, but stay tuned for more on Flash and Supergirl’s musical team-up.
For what it’s worth, neither Supergirl nor The Flash have undergone many major costume changes in the last few seasons (at least compared with Arrow), something Grant Gustin has expressed interest in rectifying.
Also lending their voices will be Jesse L. Martin, Carlos Valdes and Jeremy Jordan, along with Legends of Tomorrow stars Victor Garber and John Barrowman.