Two harpists performing together on the same stage is hardly a rarity; much orchestral music calls for two. Hearing three great harpists playing as a trio is real rarity. This extraordinary event, the brainchild of Pro Musicis, was held at Longy’s Edward M. Pickman Concert Hall on Sunday, April 25. The three harpists, Nancy Allen (Principal Harp of the New York Philharmonic), Jessica Zhou (Principal Harp of the Boston Symphony), and Mariko Anraku (Associate Principal of the Metropolitan Opera Orchestra), had each been Pro Musicis Award Winners (1982, 2001, 1993, respectively) and Ms. Anraku and Ms. Zhou were friends from their years at Juilliard, where they studied with Ms. Allen.

Pro Musicis is a uniquely wonderful organization which “nurtures” young musicians by presenting them in prestigious venues, while also requiring that they share their gifts by playing a community concerts in prisons, hospitals, shelters for the homeless — wherever “the healing gift of music is needed.”

The logistics for such a concert, with two harpists working in New York and the third in her first year in Boston, were daunting. While the three harps — two very new and stylistically different Lyon and Healy harps and a much older gold Horngacher harp — looked rather odd together, their sounds matched rather well. And all three instruments miraculously stayed in tune.

The first half of the program, duos played by Ms. Anraku and Ms. Zhou, was glorious. Cesar Frank’s ravishing Prelude, Fugue and Variation, Op. 18 transcribed by the late Dewey Owens, a harpist and organist, has for 30 or so years been a mainstay of harp duos. Mr. Owens did many transcriptions, but this is by far his most lasting contribution to the repertoire for either one or two harps. The wildly virtuosic Grand Duet for Two Harps in E Flat Major by the Welsh harpist and composer John Thomas (1826-1913, harpist to Queen Victoria) was given a brilliant performance by musicians who were clearly kindred spirits. The two then played their own arrangement of Maurice Ravel’s enchanting Suite from Mother Goose, originally written for two young children, Mimi and Jean Godebski, in 1908. There have been many excellent transcriptions of these charming pieces (Ravel orchestrated them in 1911); this was a lovely arrangement, beautifully played.

After intermission, each harpist performed a piece from her native land. Ms. Anraku played the most beloved Japanese folksong “Sakura Sakura” in an arrangement by Josef Molnar. Ms. Allen played her own teacher Marcel Grandjany’s “The Colorado Trail,” which she explained was based on an 1850 Steven Foster song, “Camptown Races.” The most memorable was the haunting “Spring on the Moonlit River” transcribed by a Chinese harpist Xie Ze-Zhi, in which Ms. Zhou evoked a far away world of colors, moods and longings.

Finally, the three harps had their moment, thanks to Nancy Allen who deftly transcribed several of her favorite pieces for this concert. A Presto in C Major by Francis Poulenc was followed by Bartok’s Hungarian Dances (originally entitled Hungarian Peasant Suite) and a seguidilla by Albeniz. Suffice it to say, most of the large audience would have been happy to have stayed and listened for another hour. That’s the highest praise one can offer about any concert, and unimaginable at a “normal” harp recital.

Susan Miron is a book critic, essayist, and harpist. Her last two CDs featured her transcriptions of keyboard music of Domenico Scarlatti.