In next week's episode of "Once Upon a Time," viewers will be treated to a new experience as they watch their favorite characters sing throughout the episode. Episode 20 of "Once Upon a Time" season 6 will be called, "The Song in Your Heart."

According to TVLine, when the episode was filmed, it felt like they were filming the very first episode for "Once Upon a Time." The cast members overjoyed to film a musical episode that they believe fans of the series have been waiting for this whole entire time.

While some of the cast members were worried about how well they would do with singing, two of lead actors did not fret about being able to deliver musically. Jennifer Morrison, who plays the role Emma, and Colin O'Donoghue, who plays the role Hook, came from musical backgrounds, so it was able to work out perfectly for them. It also helped that the episode revolved around Morrison and O'Donoghue's characters' wedding, providing them more chances to sing their hearts out.

When Lana Parrilla, who plays the role of the Evil Queen, was asked about the how "Once Upon a Time" viewers will react to the musical episode, she answered, "They're going to love it."

Based on the promo trailer for next week's episode, the episode will lead to the wedding of Emma and Hook. Emma seems to have gotten her happily ever after that Mary (Ginnifer Goodwin) wished for at the beginning of the trailer. Mary was seen looking out into the balcony and wishing upon a star to have whatever Emma needed for her happiness.

The promo trailer also shows the explanation on why the characters are singing their hearts out throughout the episode, as the Evil Queen mentions that a spell was cast on them, causing them to sing.

The episode is scheduled to air on ABC on Sunday, May 7, at 8 p.m. EDT.