Sometimes, at a concert by the orchestra of the Curtis Institute of Music, an astonishing single voice — a violinist, an oboist — will rise up from within the ensemble with great charisma and individuality. But any sense of a collective orchestral personality varies, dependent mostly on who is standing in front of the ensemble.

On Sunday night, it was Osmo Vänskä. Conductor and ensemble melded into a unified, searching interpretive spotlight in the group's last Verizon Hall concert of the season. The amalgamation promises to deepen as Vänskä — music director of the Minnesota Orchestra — embarks with the Curtis orchestra this month on their European tour to Berlin, London, Vienna, Helsinki, and other cities.

They're taking along a wild card. Peter Serkin, the school's favored son (and 1964 graduate), will join them in the Brahms D Minor Piano Concerto. Serkin, 69, introduces an unstable element to any collaboration, and Sunday night's Brahms was indeed out there — not always, but often.

Never has he been more welcome. The piano world is well stocked with players of perfect technique and polish.  But the current pipeline of teachers, agents, and others is not set up to cultivate rugged individualism of his sort.

Serkin's specific choices of tempos, dynamics, phrasing, and rubato in the Brahms concerto were sometimes odd. There were transitional spots in the first movement where you were sure pianist and orchestra could not possibly end up at an arrival point at the same time, and yet, thanks to Vänskä, they did.

It was not a fully cohesive performance, but something much better, full of imagination and questioning.

The second movement was a piece in itself, wrought of huge contrasts. A few minutes in, Vänskä reduced the string sound to a breathy whisper, setting up a remarkably touching moment for Serkin's entrance. The presence of these two big personalities had a salutary effect on the orchestra. The leaders took risks, and so did the young musicians, paying off with unusually stylish phrasing in the woodwinds.

It's understandable that the Barber Adagio for Strings would be a good calling card for Europe, where it may end up as an encore. In Philadelphia, though, we hear a lot of Barber, and, for a concert as long as this one was, the piece seemed extra, even led sensibly as an opener by conducting fellow Conner Gray Covington.

Vänskä had a lean, incisive vision for Strauss' Ein Heldenleben. This was a performance of great intensity — not just because of some impetuous tempo changes and smart emotional pacing, but also through the lustrous ensemble sound the conductor had obviously cultivated. Concertmaster Maria Ioudenitch was as a fully formed professional in tending to both warmth and virtuosity in her sprawling solo work, and oboist Virginia McDowell was sweetly penetrating. The conductor had the trust of the orchestra, and charisma bloomed.

The orchestra of the Curtis Institute of Music performs works of Barber, Beethoven, Bernstein, and Ravel May 13 at 7 p.m. in a free concert at the Mann Center. Curtis conducting fellows Carlos Arango Agreda and Conner Gray Covington conduct.