The Sunday fest had Broadway stars singing show tunes, pop covers and Disney hits amid a beer garden, food trucks, meet-and-greets with performers and a Marie’s Crisis piano bar.
Read more Inside Darren Criss' Plan to Create an Annual Music Festival With Broadway Performers
Lea Salonga, currently starring in George Takei's new musical Allegiance, kicked off the outdoor music fest.
Fest creator Darren Criss joined Salonga onstage for "A Whole New World" from Disney's Aladdin, in which she played the singing voice of Jasmine. "It was so fun to watch people while they were performing, turn and go, 'Oh my god, this is amazing,'" Criss told THR. "When Lea Salonga is at Carnegie Hall and they want to sing along and shout, they have to sedate themselves for the environment. And these kids were going ape shit!"
Criss also joined his band Starkid, who originated the viral hit A Very Potter Musical.
Said Criss after the fest, "I was afraid we wouldn't be able to hold people's attention. The thing about musical theater's performers is that's what they do! They capture people's attention."
Read more Inside Darren Criss' Plan to Create an Annual Music Festival With Broadway Performers
The actor and radio host performed his humorous and elaborate theater deconstructions for the crowd.
The actress, who will star in The Bandstand at Paper Mill Playhouse, reprised songs from her previous Broadway role in Cinderella in a medley with a song from Stephen Sondheim's Into the Woods.
Fellow performer Aaron Tveit joined her onstage for a duet on "Falling Slowly" from Once. During his set, Osnes accompanied Tveit on "As Long as You're Mine" from Wicked, in which he played Fiyero.
The actor sang musical numbers from Next to Normal, Miss Saigon and Catch Me If You Can.
"I'm truly beside myself," said Criss after the fest. "Aaron Tveit was a rock star while singing Wicked!"
Read more Inside Darren Criss' Plan to Create an Annual Music Festival With Broadway Performers
Tveit, who will play Danny in Fox's Grease, also covered Bruno Mars, Coldplay and Taylor Swift.
The Hamilton star kicked off his set with a jazz band-backed rendition of the show's standout track, "The Room Where It Happens."
He then performed songs from his previous show Jersey Boys and shared a steamy cover of Selena Gomez's "Good for You."
Throughout his set, Criss performed tracks from Mulan, How to Succeed Without Really Trying, Cabaret, Les Miserables and Hedwig and the Angry Inch.
The final set's guests included Neon Trees' Tyler Glenn for "Animals" as well as A Great Big World duo Ian Axel (pictured) and Chad Vaccarino for a harmonious "Beauty and the Beast."
"I'm very amazed at everyone's enthusiasm," Criss told THR after the long day. "The second I walked in, there were a million things I wish I could've done, but it's all a learning process. If my losses were less than my extraordinary gains, then I'm fine."