In the second concert of its 2018 season of fine music at St. Paul’s, the Impromptu Classical Concerts again virtually packed the church’s generous seating space. Featured last Sunday afternoon: the heroic cello playing of a young musician, Jacob MacKay, this year’s front-runner in the Impromptu’s ongoing Rising Star series.

With the very first notes of a melody-rich program, mainly of romantic music, the handsomely boyish MacKay asserted a bold, charismatic mastery of the cello. His opener, Mendelssohn’s Song Without Words op. 109 was presented with uncommon energy. And the depth and richness of his tone continued through five extended folk-music-flavored works by Robert Schumann, all delivered with confident bravura. MacKay’s accompanist, pianist Charles Tauber, played with due power and sensitivity, but was rarely able to shift attention from MacKay, a musician with a remarkable future.

Graduating from Brandeis University Summa Cum Laude just two years ago, MacKay has already performed as soloist, chamber musician and orchestra member throughout the United States, Europe and the Middle East. After a well-received trip to Jerusalem last year, he plans to return again next year with hopes of taking his cello to other corners of the world. “If you give me the plane ticket, I’ll go anywhere,” he said.

Sunday’s program continued with Three Meditations from Mass by Leonard Bernstein. Celebrating the centennial of Bernstein, the Impromptu is showcasing some of Bernstein’s music in each of its seven concerts of 2018, and MacKay’s Meditations selection offered intriguing contrast to the buoyant opening works of the afternoon’s concert.

The Meditations were brooding and ambiguous, with tensions in place of the songlike charms of the opening works. MacKay’s cello was in full-toned but subdued mode, peacefully making the most of unexpected opportunities to offset the music’s moody twists and turns with quiet queries and reassurance.

Rachmaninoff, all flags flying, filled the entire second half of the program, and MacKay’s muscular tone rose triumphantly to the occasion. George Korn, Impromptu Concerts president, had remarked in intermission comments that the Rachmaninoff’s brilliant Sonata in G minor could be termed a sonata for two instruments, not merely for cello with piano accompaniment. This was “a sonata for two separate but equally important instruments, a cello and piano,” noted Korn.

MacKay and Tauber each vied, appropriately, for the audience’s attention, but Tauber’s most spirited fingerwork was inevitably upstaged by MacKay’s stormy, passionate cello. At the conclusion of Rachmaninoff’s powerhouse Sonata, the audience gave the beaming MacKay and Tauber a thunderously well-deserved standing ovation.

Next Impromptu Concert at St. Paul’s will be Sunday afternoon, Feb. 11, with the internationally acclaimed a cappella vocal sextet The Western Wind in their third Impromptu appearance.

Impromptu Classical Concerts tickets are reasonably priced at $20, students free – at the door, or via keystix.com (2295-7676). Concerts start at 4 pm, please come early for preferred seating.