For fans of The CW (and of a good sing-a-long), there’s some exciting times for The CW’s DC characters. Not only has Melissa Benoist’s Supergirl now joined the network’s DC realm, but there’s two crossovers coming up that involve the Maid of Might, one of which is a musical crossover with Grant Gustin’s Flash. We’ve known about those before, but now executive producer Greg Berlanti has been giving an update on what to expect from this musical event as well as the bigger crossover that will arrive later this year.

Speaking to IndieWire about the musical crossover between The Flash and Supergirl, Berlanti said, “We just finished writing the fall crossovers, and now we’re trying to figure out how to produce them. That’s probably the most challenging thing we do all year. And now we’re doing it across three shows. But next week we’ll have to start talking about clearing music. I have a few ideas for tone and style in my head, but we’re just starting to talk about what that can be. I do want to try and get an original piece of music written. As we make a deal on that we’ll probably make some announcements on the original songs.”

It was previously believed that Joss Whedon may actually be in the frame to come in and oversee the musical crossover, although there’s nothing confirmed on that front. When asked about who they’ve been talking to for this crossover, Berlanti teased that they “did speak to someone we’re really excited about. There are some writers I’m incredibly excited to work with.”

Moving on to the larger crossover that will take in characters from Arrow, The Flash, DC’s Legends of Tomorrow and Supergirl, Berlanti added, “You really are trying to run a single production across three different productions. But they’re run as three separate entities. We have to figure out when we’re borrowing one actor from where. We’re telling one cohesive story; Supergirl will participate, but the storyline doesn’t actively being there. There are some characters who show up in her episode, but the story begins with The Flash episode goes to Arrow and Legends of Tomorrow. We’re just getting into designing the bad guy for it, and we start now but it doesn’t air until the end of November. We will put a lot of time between now and then figuring out visual effects sequences. Just today I was holding the three scripts back-to-back – that’s 180 pages of material. It’s a three-hour story, almost a miniseries”.

Arrow, The Flash, DC’s Legends of Tomorrow and Supergirl all return to screens next month.