A two-part ‘Supergirl’ and ‘The Flash’ musical crossover episode is coming
Thursday, August 11, 2016 at 6:16PM 
The Flash and Supergirl are teaming up again. This time, it’ll be for a two-part musical episode. Yes, a musical. Since Supergirl moved from CBS to CW, it’s expected that the DC adaptations, including The Flash, Arrow, and Legends of Tomorrow, will be working alongside its newest sister. In fact, they do have a big crossover in the works. But that’s for another time. Right, now we’re getting that two-part musical.
It doesn’t come as a surprise they’re trying this route since a lot of the actors on Supergirl and The Flash have musical backgrounds. Yes, that includes both shows lead actors Melissa Benoist and Grant Gustin. Both of them have appeared on Glee. Jesse L. Martin (Joe West on The Flash) originated the role of Tom Collins in Rent on Broadway. Jeremy Jordan (Winn on Super girl) has also appeared on the Broadway production of Newsies. According to Greg Berlanti, the executive producer of all DC shows on CW, the songs will mostly be “preexisting songs” but they are working to include at least one original track per episode. Speaking at the Television Critics Association press tour, Berlanti says these episodes are likely to air sometime in the “back half of the year.”
Source: The Verge