The conductor onstage was so familiar to the audience that he might as well be family, though he was surrounded by musicians who were completely new to the Kimmel Center’s Verizon Hall.

Somehow, you could tell that they were all family, when the Orchestre Metropolitain de Montreal made its Philadelphia debut on Sunday under Yannick Nézet-Séguin, who has led the orchestra since 2000 (starting when he was only 25) and is continuing with a recently announced lifetime appointment. The orchestra existed before him, but he basically built it into an ensemble rivaling the world-class Montreal Symphony Orchestra — on a good night.

This relatively young group hasn’t yet rock-solid consistency, but in this U.S. tour, the musicians’ rapport with Nezet-Seguin counted for much in a concert of Bruckner’s Symphony No. 4 and Mozart arias with mezzo-soprano superstar Joyce DiDonato. Some moments felt like a single brain with 200 accomplished arms, as orchestra and conductor negotiated subtle shifts of tempo and volume, some more felt than heard, that pulled you further into the music’s inner workings and mysteries.

It was also a great day for DiDonato. She and Nézet-Séguin seem seriously joined at the hip these days, performing Schubert’s Winterreise on Dec. 8 in Montreal and Dec. 15 at New York’s Carnegie Hall with an unorthodox approach: Typically sung by men, this song cycle about a heartbroken man going out into the snow to die is being sung by DiDonato, this time as the recipient of what amounts to suicide dispatches in song. Then, later on in the season at the Metropolitan Opera, they’ll collaborate on Massenet’s equally suicidal Werther. But they certainly had fun together on Sunday with excerpts from Mozart’s oddly neglected, late-period opera La Clemenza di Tito. First came the overture, and then DiDonato went character hopping, encompassing the outsized emotions of the ancient Roman ruling class with “Parto, parto, ma tu ben mio” and “Non piu di fiori.” As an encore, she portrayed the gawky teenager Cherubino in the aria “Voi Che Sapete” from the Marriage of Figaro.

The Tito arias make the singer do everything: Ponder, react, be emotionally volatile, and sing complex coloratura while dueting with clarinet. Mozart loved taking singers into the stratosphere, but also demanded dramatic weight in the lower range, for which the normally lean-voiced DiDonato demonstrated a level of power and vocal richness I haven’t previously heard from her. Some divas lapse into autopilot or mannerism at this stage of their careers; DiDonato keeps going further and deeper into whatever she is doing. In the Tito arias, soloist Simon Aldrich played with wonderfully restrained lyricism on both clarinet and the deeper-toned basset horn.

The Bruckner Symphony No. 4 raised particularly rich questions. Nézet-Séguin, has a long history with the piece, both with the Philadelphia Orchestra and Rotterdam Philharmonic (from which he recently departed). He’s a conductor who prides himself at collaborating with any orchestra’s institutional history, so Bruckner performances with the Philadelphia Orchestra capitalize on the monumentality that’s possible with the ensemble’s sound. But in Montreal, he is the institutional history.

What does that sound like? Nézet-Séguin’s 2011 Montreal recording had crisp rhythms unusual for the massive sonorities of Bruckner. Now, rhythm is less pointed, but still has a distinctive lift that circumvents the piece’s tedium potential. Often, Bruckner is heard as blocks of sound; Nézet-Séguin prefers something with a more Wagnerian flow of musical events with transitions that were masterfully handled by conductor and players alike. The orchestra also generates a proper Brucknerian roar, which definitely matters. For the record (and for the sake of us Bruckner nerds), Nézet-Séguin used the Haas edition of the symphony -- which also matters.