Portland Ovations has brought many outstanding pianists to Merrill Auditorium over the years, but the performance of Imogen Cooper on Wednesday night made me reach for the thesaurus to look for new superlatives.

She is that rara avis of a virtuoso who is also a consummate musician; one who thinks deeply about the composer’s intent and realizes it with insights that weren’t available when the work was written. Haydn would have been delighted with her reading of his Sonata in E-flat Major (Hob. XVI/52) and amazed at its power on a concert grand.

That particular sonata, which could aptly be labeled “The Appoggiatura,” demonstrated Cooper’s ability to combine clear articulation with velocity and dramatic mood changes. It also revealed an innovative composer for the piano, who was Mozart’s equal, if not his superior.

Even more than the Haydn, the Drei Klavierstucke (D. 946) of Schubert showed Cooper’s uncanny control of sonority and inner voices. Published posthumously, these three impromptus seem intended to carry on the legacy of Opus 90 and Opus 142. They are not heard as often, which is a shame, because they break new ground without losing any of the genius of the first two collections.

No. 1, in E-flat minor, at first seemed too fast, but it was soon obvious that the chosen tempo was perfect for the realization of the development. The second impromptu, in E-flat major, with its plaintive theme reminiscent of “Lily Marlene,” added a delicate feeling for melodic line to the roster of Cooper’s accomplishments.

The final piece, in C major, showed Schubert at his most dramatic and least likable, with its rapid skewed rhythms and violent contrasts. Cooper made it sound as good as possible.

After intermission came Brahms’ Theme and Variations on a passage from the second movement of the String Sextet, Op. 18. Written as a birthday present for Clara Schumann, they are on the same level as his Variations on a Theme of Handel, without being quite as comprehensive or inventive. One variation shows Brahms in a playful mood, converting the somber theme of the Sextet into a music box tune.

From the Brahms, Cooper segued directly into the Beethoven “Tempest” Sonata in D Minor, Op. 1, No. 2, leaving no room for distracting applause. During the familiar passages of the sonata, I wondered what it was that made Cooper’s playing so unusual, and settled on the word “richness.” Everything she plays, from a simple chord to a rapid cadenza, seems to have an orchestra behind it. The inner voices weave some sort of magic.

Cooper does not seem to be noted as a Chopin specialist, but her versions of the Nocturne in D-flat major, Op. 27, No. 2, and the Ballade in G minor, Op. 23, were among the best I have heard — tremendously exciting, brilliant as fireworks, but with meaning beyond mere display.

The pianist did not play an encore, despite a rousing standing ovation, but what possibly could have topped the Ballade?

Christopher Hyde’s Classical Beat column appears in the Maine Sunday Telegram. He can be reached at:

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