The pianist Garrick Ohlsson has been demonstrating his credentials as a Romantic powerhouse this season, with arresting performances of Liszt in honor of that composer’s bicentennial. He gave a Liszt recital at the 92nd Street Y in January and will perform a variation on that recital at Carnegie Hall on April 29.

On Thursday evening at Avery Fisher Hall, Mr. Ohlsson showed his skill as a Classicist, when he joined the New York Philharmonic, conducted by Herbert Blomstedt, in Mozart’s Piano Concerto No. 9 (“Jeunehomme”).

Mozart’s talent as a composer revealed itself early, but his teenage works weren’t as sophisticated as Mendelssohn’s. Mozart wrote this concerto at 21, and many consider it his first masterpiece. The pianist Alfred Brendel has called it “one of the greatest wonders of the world,” unsurpassed even by Mozart’s later concertos.

The nickname refers to a Mlle. Jeunehomme, for whom Mozart was thought to have written the work, although some scholars now believe it was written for a woman called Jenomy. Mozart broke new ground by having the piano share in the opening theme and with the unusual structure of the concluding Rondo.

Mr. Blomstedt, the conductor laureate of the San Francisco Symphony, led a lithe, supple interpretation with a reduced orchestra. Mr. Ohlsson played with fluid touch and graceful phrasing throughout, particularly admirable in the dark-hued Andantino. He performed the cadenzas Mozart provided with flair.

After intermission came Tchaikovsky’s Symphony No. 5, which that always insecure composer deemed a failure. He wrote to his patron, Nadezhda von Meck, that he saw “something repellent” in the work, which he feared would never please audiences.

He could not have been more wrong; the symphony has long been a crowd-pleasing war horse. Mr. Blomstedt, conducting without score, led a tightly wrought interpretation that reveled in the music’s majestic elements without ever succumbing to sentimentality.