The third annual Encores! Off-Center series, in which noteworthy Off-Broadway musicals are performed concert-style at City Center, gets off to a smashing start with a new staging of William Finn's ("Falsettos," "Spelling Bee") dynamic, eccentric and emotional 1998 piece "A New Brain" led by Jonathan Groff, Ana Gasteyer and Dan Fogler.

Based loosely on Finn's own medical trauma, it observes how Gordon (Groff), a young, gay, professionally frustrated, somewhat conceited musical theater songwriter collapses one day and is rushed to the hospital, where he finds out that he needs immediate brain surgery.

As he awaits the operating table, Gordon converses uneasily with his frenzied mother (Gasteyer), calm and collected boyfriend (Aaron Lazar) and Mr. Bungee (Fogler), the demonic host of a children's television show that Gordon writes songs for.

The unpredictable, often catchy score alternates between madcap, hallucinatory production numbers and gorgeous, tender ballads.

The original Off-Broadway production received only a short run at Lincoln Center Theater. Given the unexpected success of "Fun Home," another musical featuring unlikely subject matter and a dysfunctional family, a larger audience may finally be ready to embrace "A New Brain."

The current production (directed by James Lapine) has very little scenery, which makes it look rather empty in the big theater. Nevertheless, the musical plows ahead without pause for 100 minutes and giddily sweeps the audience along.

Groff, who rose to fame as the male lead of "Spring Awakening" before appearing on television in "Glee" and "Looking," brings a sensitive aura and sings beautifully, but he glosses over Gordon's overanxious and uneasy personality.

Gasteyer is in superb form as Gordon's volatile mother. Rema Webb is also terrific as a homeless woman who stops the show with one of the musical's most clever and overtly political songs.

If you go: "A New Brain" plays at City Center through Sat. West 55th Street between Sixth and Seventh aves. NYCityCenter.org.