Mr. Hamelin enjoys unearthing rare scores in secondhand shops. But the demise of brick-and-mortar outlets has meant fewer opportunities to discover gems.

Some works, like Dukas’s mammoth Piano Sonata, Mr. Hamelin said, fell into obscurity because they were never promoted by a big-name exponent. Mr. Hamelin grew up listening to recordings by golden-age pianists, many of whom — like pianists in the 19th century — played their own arrangements and compositions.

Mr. Hamelin’s 12 Études, in all the minor keys, which he performed at Le Poisson Rouge in September (and which have been published by Edition Peters), were inspired mostly by 19th-century composers and writers. The poetic Étude No. 7 in E flat minor (“After Tchaikovsky,” for the left hand alone), for example, is modeled on Tchaikovsky’s “Lullaby” (Op. 16, No. 1). The Étude No. 3 in B minor (“After Paganini-Liszt”) takes its inspiration from “La Campanella,” and the Étude No. 8 in B flat minor (“Erlkönig, After Goethe”) mirrors Goethe’s famous poem.

Composing, transcribing and arranging are now mostly lost arts for pianists, Mr. Dubal said, praising Mr. Hamelin’s eclectic interests and talents. Composition, Mr. Dubal added, should be encouraged in conservatories to facilitate broader and more creative artistry, rather than the “robots culture, a mechanical culture” that exists today.

“Just because you can play the octaves of the Tchaikovsky Concerto,” Mr. Dubal said, “you can’t expect to be called an artist or a musician. I’m adamant about that. I teach many pianists at Juilliard, and it doesn’t mean they will ever be artists or even musicians.” To be a complete musician like Mr. Hamelin, “you have to learn how to compose, how to transcribe, how to arrange music,” he added. “It’s all part of a great tradition.”

That tradition has faded because of changes in conservatory training leading toward a system that encourages rote study and memorization of large segments of the mainstream pianistic repertory. “It’s much more important than many students realize to have a thorough grounding in harmony, counterpoint, theory and ear training,” said Mr. Hamelin, who studied at the École de Musique Vincent-d’Indy in Montreal and received undergraduate and graduate degrees in piano performance from Temple University in Philadelphia. “Without that you will be a very incomplete musician.”