Days after winning two 1992 Tony Awards for “Falsettos,” composer William Finn was diagnosed with a terminal brain condition. Fortunately, the initial diagnosis was incorrect and after some tricky surgery, Finn emerged healed and healthy. He would go to write the popular “The 25th Annual Putnam County Spelling Bee.”

The near-death experience, however, left a strong impact on him.

“When I came out of the hospital, I couldn’t sit at the piano without writing a decent song,” said Finn. “There was just all this gratitude that I was alive and this life spewing out of me — the piano was singing — and I was just there to write it down.”

Along with his longtime collaborator, James Lapine, Finn put all his joy, gratefulness, fears and hopes into “A New Brain,” a heartfelt celebration of second chances, now being given a terrific, rousing and relentlessly enjoyable production directed by Christopher Bentivegna at Kajun’s Pub.

This 90-minute, offbeat musical revue is Finn’s autobiographical rendering of his transformational struggle.

Gordon Schwinn — Finn’s onstage alter ego (Chris Wecklein) — hates his job of composing insipid ditties for Mr. Bungee (Kyle Daigrepont), a frog-garbed host of a children’s television show called — “Mr. Bungee’s Lily Pad,” when while lunching with friend Rhoda (Lisa Picone), Gordon collapses.

At the hospital, Dr. Berensteiner (Price Provenzano) delivers the shocking news that Gordon’s cranial disorder demands a dangerous surgery which may prove fatal. Gordon fears he will die with his best music yet to be composed. Surrounded by nurses (Janie Heck, the Thin Nurse and Nethaneel Williams the Nice Nurse), a minister (Nick Stephens) and comforted by his mother, Mimi (Tracey Collins) and his lover, Roger (Robert Facio), Gordon falls into a coma after the operation.

While unconscious, Gordon dreams a musical featuring various friends and acquaintances.

What follows is a non-linear, hallucinatory tribute to regeneration and renewal.

Bentivegna has assembled an absolutely top-notch cast. Every member fits their role perfectly, with each getting a moment to shine, either in a powerhouse solo or in one of the many exhilarating group numbers.

Wecklein amazes. So fully invested is he in his portrayal of Gordon that it’s hard to imagine anyone else in the part.

The honesty he brings to such songs as “911 Emergency/I Have So Many Songs” and “Heart and Music” endearingly electrifies.

All the numbers are well sung and completely unpretentious, but several stand out. As Lisa, an enigmatic homeless person, Jessica Mixon brings the house down with her impassioned rendition of “Change.”

Collins’ unforgettable delivery of “Music Plays On,” a song voicing every mother’s terror, is so truthful and appealing you don’t want it to end.

Perhaps Finn’s greatest song goes to the superb Facio, with his impeccable performance of the ballad “Sailing.”

Kajun’s very intimate barroom venue presents a challenge for director and audience.

The action is literally in your face and all around you. Somehow, this heightens the experience rather than distracts.

Amanda Zirkenback proves she can create witty, entertaining choreography in a space the size of a postage stamp.

Except for some unnecessary audience interaction at the beginning, Bentivegna’s tight, big-hearted production contains not one false note.

The real star of the evening is music director Ainsely Matich and her brilliant vocal arrangements. Accompanied by a splendid three piece band — Matich on keyboards, Aaron Welker on percussion and Benjamin Reinhardt on violin — the rich sound of the live and unamplified voices dazzles.

This is a must-see, life-affirming gem of musical theater that triumphantly dramatizes Finn’s assertion that “You have to greet each day with enormous gratitude and hope and happiness.”

Bruce Burgun is a retired theater professor from Indiana University and is a member of the American Theatre Critics Association.