Once Upon a Time: Everything tu need to know about the musical episode 

We know Emma and Hook are getting married in the upcoming musical episode, but what we don’t know quite yet is

executive producers Adam Horowitz and Edward Kitsis to get some answers.

But first, here’s what we know so far: The musical hour, which will air Sunday, May 7 at 8 p.m. ET on ABC, is titled “The Song in Your Heart.” As we previously revealed, the hour will feature seven original songs from Alan Zachary, Michael Weiner, and

Among those singing during the episode are Emma (Jennifer Morrison), Regina (Lana Parrilla), Hook (Colin O’Donoghue), Charming (Josh Dallas), Snow (Ginnifer Goodwin), Zelena (Rebecca Mader), Henry (Jared Gilmore), Granny (Beverley Elliott), Grumpy (Lee Arenberg), Geppetto (Tony Amendola), and more. Here’s what else you need to know:

ENTERTAINMENT WEEKLY: Why is everyone breaking into song?

ADAM HOROWITZ: What we can say is that we want to keep the machinations a little bit of a surprise, but that it’s key to Emma’s journey — the journey that began in the pilot and that we’ve seen throughout the whole series. The singing and the musical is tied directly to Emma.

EDWARD KITSIS: At the beginning of the year, we met with these composers, Alan and Michael, who we love. When we started talking about the musical, we wanted it to be a special episode. We thought Emma’s wedding felt like the natural milestone for us.

HOROWITZ: It felt like the right place. Hopefully, when you see how the device works within the episode and how it relates to Emma and her character journey, it all seems to make sense that it would lead up to this. It worked on both a plot and character level, and it allowed us the fun of actually doing a musical episode.

KITSIS: One of the fun things about a musical is you emotionally say what you’re thinking in song. For Emma, who has been a very guarded and walled-up person, the wedding signifies the growth of her being able to trust someone again and letting her walls down, so we felt like the musical was perfectly a match with that.

HOROWITZ: All the songs in the musical are designed — and we hope this audience feels this way when they watch it — to not be to just stop and have a song; they’re designed to actually reveal character and move the story forward. Each song is constructed in a way that’s dealing with what’s going on with the characters and what’s going on with the story. We’re trying to move toward something. It builds to that wedding, which — like everything in the episode — we hope is filled with a few other surprises.

What can you tease for some of the songs we’ll be hearing?

KITSIS: The songs are all original. They’re specific to each character. Hook’s song, and the Evil Queen, Snow and Charming, it’s like their episodes all individually have their own tone to them, I think the songs are as well.

HOROWITZ: Stylistically, each song is suited to the character’s journey, so that when we see Hook singing, we can say that song does take place in a flashback, and it fits tonally in what a pirate would be thinking and what Hook would be thinking and therefore singing at the time we see him, which is kind of a pirate with a dark streak. In the same respect, when we see Snow and Charming’s song, there’s a duet and a true love element to it. Through all of them, we try to have the songs and the style of the songs tie into who the characters are and what they’re going through. The composers did an incredible job. These songs surpassed our expectations when we heard them, and then when we heard our cast and what they could do with them, it surpassed even further. So we’re really excited about it.

HOROWITZ: Yeah, these are really fun, catchy, cool songs, and different styles from a ballad to real rock & roll to all sorts of stuff.

Are the characters aware that it’s odd that they’re singing? Do you go meta in that sense?

HOROWITZ: Yup, it’s not just like singing and nobody acknowledges that songs are happening. They definitely acknowledge that there is singing going on and that it’s an unusual development, because through the previous 130 episodes, there hasn’t been singing.

When it came to singing and dancing, was there anyone in the cast who surprised you?

KITSIS: That is a really tough question because we knew the ones that were singing all had musical theater backgrounds.

] No, we kind of went in knowing, but I’ll be honest, about a month before, Ginny [Goodwin] kept saying, “Oh, I can’t sing, I can’t sing,” and then when we heard her voice, we were like, “Why did you lie to us?” So I went in thinking, “Well, every time she sings happy birthday, it sounds great,” but she kept saying she couldn’t sing, and then when we heard her, it was phenomenal. I was only surprised in the sense that she told us she couldn’t and she could, so we have to call her out as a liar here at EW. She can sing!

One question that’s come up a lot: Is Rumple going to sing?

KITSIS: For that, we’ll have to wait until the musical airs!

Read our postmortem with Rebecca Mader on Zelena’s sacrifice here.

1 \'Feud\': Ryan Murphy talks \'Bette and Joan\' finale, \'super juicy\' season 2

2 \'Wizards of Waverly Place\' cast reunites for David Henrie\'s wedding

3 \'Once Upon a Time\' star Rebecca Mader on Zelena\'s sacrifice

4 \'13 Reasons Why\' cast talks hope for a potential season 2

5 \'Happy Days\' star Erin Moran dies at 56