In 1968, however, Bilson was hired at Cornell University, where he met antique instrument builder Philip Belt. Belt introduced Bilson to the fortepiano, the instrument for which Mozart's sonatas and concertos were written. Quieter and less resonant but more agile than a modern grand, the instrument bowled Bilson over musically. "It was the first time I'd been able to play every note Mozart had written," he explained. "The modern piano develops the tone slowly and is ideal for long, gradually unfolding lines but poor for phrases containing frequent changes in stress." He began performing on the fortepiano, at first mostly in university settings, and then, as the authentic performance movement grew to encompass music of the Classical era, on the concert stages of the world. He toured with cellist Anner Bylsma and made numerous recordings, including a complete set of Mozart's piano concertos on which he was accompanied by the English Baroque Soloists and conductor John Eliot Gardiner, for the Deutsche Grammophon label.
Like other period instrument performers, Bilson in the 1990s and 2000s became interested in music of the early 19th century. In 1994 he and his students presented all 32 of Beethoven's piano sonatas in concert in New York, perhaps the first time they had been played together in public on instruments of Beethoven's time since they were composed. In the estimation of The New York Times, "what emerged in these performances was an unusually clear sense of how revolutionary these works must have sounded in their time." Freely giving his time to chamber music and vocal performances as well as his own solo career, he often worked with Gardiner's Orchestre Révolutionnaire et Romantique. Bilson's activities in 2004 included a group of appearances at Hungary's Sopron Early Music Days festival., Rovi