A short-notice casting change proved the highlight of the Metropolitan Opera’s season premiere of Giacomo Puccini’s “La Bohème” on Saturday afternoon. Since most of us believe that Musetta is the juiciest part of this opera, soprano Patricia Racette’s appearance in the role, in place of an ailing Susannah Glanville, was a fortuitous inclusion.

“Quando me’n vo’ soletta per la via” should be the number that stands out in the mind’s ear and Ms. Racette made the most of it. A supremely confident grisette, she plunges off of a table at the Café Momus knowing that she will be caught by uniformed chorus boys. She has that je ne sais quoi that transports this waltz onto a higher plane, a musical vignette out of place and time, elevating her role to that of raisonneur. Everyone else seems small in comparison.

Ms. Racette was an instant success in the role, at one point fashioning such a delicious diminuendo that a lone cry of brava led to an extemporaneous ovation mid-melody. This was certainly the pivotal musical moment of the piece, and Ms. Racette sang it with scope and brio, but I wished for more of an arrhythmic quality to the melodic line — a touch of rubato and a soupçon of Viennese color. With Placido Domingo in the orchestra pit, though, we were lucky to have any sense of orchestral shading whatsoever. Though a splendid musician, Mr. Domingo may be better suited for arts administration going forward. Thus far, he has shown little flair for the subtleties of the podium.

The headliner everyone had paid to hear was the Mexican tenor Rolando Villazon, who rather curiously held back for quite a bit of Act I. When singing Otello or Siegfried it might be necessary to save one’s voice for later, but as Rodolfo you might as well let it all hang out. Beginning tentatively, Mr. Villazon took virtually all of the “Racconto di Rodolfo” to warm up and let his natural sweetness flow. He is a fine tenor and projects seemingly effortlessly, but this day he only realized his full potential around the time of “Mimi e una civetta” in the snows of Act III. There was also a curious, dispassionate quality to his performance that seemed discordant with the standard emotionality of this particular character.

Angela Marambio made her Met debut as Mimi. She has the wrong voice for the role, its heftiness leaving the normally nimble phrases a bit lumpy, but she projects very well and her overall sound is, if not beautiful, at least strong. What was really missing, though, was any sense of morbidezza — that tinge of impending doom — that should at least be suggested in any good performance of “Bohème.”

Peter Coleman-Wright was a competent Marcello and more than held his own in the big quartet at the end of Act III. Aaron St. Clair Nicholson made his debut as Schaunard and Paul Plishka was a wonderful Benoit, a landlord with a heart, a strong sense of nostalgia, and a taste for a good swig of wine.

Of all of the sidemen, the most effective was John Relyea’s Colline. Already a very big guy, Mr. Relyea wore a tall hat to make himself even more noticeable, and directed the focus to his humorous pantomiming in scenes he actually made funny. A very warm and secure lower register led to a fine and noble “old coat” aria in Act IV, although just a tad more emotion from the orchestra (paging Mr. Domingo!) would have helped immeasurably.

All of this was played against that busy and overblown production. This is the one work where the New York City Opera goes head to head with the Met every season and wins hands down. At least this year, people were not walking into each other during the boulevard tableau. Many people, I am told, love this Franco Zeffirelli “Gone With The Wind” extravaganza. I, however, have never actually met any of them.

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People who love Aprile Millo really love Ms. Millo, and so interspersed among the nearly capacity crowd dressed in their finery as the National Italian American Foundation honored the soprano were the occasional young man or pair of young men tastefully outfitted in smart jeans and strategically placed around the hall for maximum claque impact. Whenever their girl appeared, there were noticeable exclamations of pure joy.

The occasion was the New York debut of tenor Roberto Iarussi, accompanied by his own personal conductor, Mark Giuliani, and the Orchestra of St. Luke’s. This kind of night is what pays the rent for St. Luke’s so it was not at its crisp best, but dutifully followed Mr. Giuliani’s rather wooden directions to oom-pah-pah its way through and not upstage the singer. This conductor appears to only know one dynamic level — a solid, if pedestrian mezzoforte — but is certainly as loyal as a bulldog to its universal application.

Mr. Iarussi possesses a powerful lyric tenor and is capable of a fine individual performance. One of the most moving tenor arias Puccini ever wrote was “Ch’ella mi creda” from “The Girl of the Golden West” and Mr. Iarussi declaimed it with a strong sense of emotion. It is a “we who are about to die salute you” type of valedictory and was even intoned by Italian troops in the trenches of the Great War. Mr. Iarussi caught just the right air of poignancy and delivered the goods effectively.

He does have some problems in his upper register, however, and perhaps should not have chosen such an ambitious aria as “La mia letizia infondere” from Verdi’s “I Lombardi.” Here he sounded quite strained as he fought in vain for those higher notes. Although I was pleased that he included, as his one non-Italian number, the “O souverain” from Jules Massanet’s magnificent and oddly underrated “Le Cid,” his flailing for the high note here again only made him go flat more than not. Still, the potential is surely there.

As for Ms. Millo, she dismissed the printed program as irrelevant and offered an entirely different couple of selections. Having just emerged from the opera house, I had to chuckle as she announced that she and Mr. Iarussi were not in fact going to sing “Viene la sera” (from “Madama Butterfly”), but rather “O soave fanciulla” (from “Bohème”). This rendition was about as different from the Villazon-Marambio as it could possibly have been, but not necessarily its inferior. Ms. Millo has a gigantic voice — too big, in fact, for Alice Tully Hall. But it is also a lovely instrument, with a rich and burnished lower register. Mr. Iarussi held his own with her, his voice nowhere as sweet and gentle as that of Mr. Villazon, but just as powerful. The pair walked offstage in each others arms during this duet, singing their last notes from the wings, as is often done in the opera house — a nice touch.

This entire evening was great fun and ended with Ms. Millo receiving the Voce D’Oro award given in honor of Renata Tebaldi, and singing a few Neapolitan songs. But the undoubted takeaway memory was her knockout version of the “Suicidio” from the Orfano Canal act of Amilcare Ponchielli’s “La Gioconda,” which she is currently singing at the Met. This is properly classified as a dramatic soliloquy, and never have I heard it sung quite this dramatically. Ms. Millo, in addition to possessing all of the requisite vocal tools, has a highly developed sense of acting. Her little pauses and flashes of the eyes were mesmerizing. This was one of those rare performances at which I heard a loud exhalation of breath at its conclusion, and realized it was mine.

“La Bohème” until February 3 (Lincoln Center, 212-721-6500).