Correction: A previous version of this article misstated the relationship between Mary Stuart, a.k.a. Mary, Queen of Scots, and Queen Elizabeth I. They were first cousins once removed, not half sisters; Elizabeth’s half sister was Mary Tudor, not Mary Stuart. This version has been corrected.

Opera is on some level a sporting event. High art, sure; but lots of its fans go to hear who will write a better piece or sing a better aria or simply to enjoy the sheer athletic ability of people who can fill a 2,000-seat hall with their voices without a mike. Opera in concert only emphasizes the genre’s sporting side. There are no sets here, and no costumes to interfere with the basic act of singing, and sound, and listening to the way one voice sounds against another, or against the voices in your inner ear.

On Sunday, the Washington Concert Opera offered something of a soprano showdown in the form of Donizetti’s “Maria Stuarda.” In fact, it was a veritable Three Ages of Sopranohood. In one corner, you had Brenda Harris as Queen Elizabeth: a veteran with a steely, capable voice, sometimes a touch shrill, sometimes a tad dry, but able at its fullest to peel paint off the walls and dwarf every other singer onstage. In the other, you had Georgia Jarman as Mary, Queen of Scots, the title role, investing every note she sang with both meaning and beauty. And hovering just outside the ropes was Alexandra Loutsion as the lady-in-waiting Anna, singing a little bitty role with a big, healthy-sounding voice, a tangible reminder of the fact that however much opera resembles organized sports, its farm system still has trouble figuring out what to do with big young voices beyond assigning them the kind of small servant roles that dotted Loutsion’s program bio and waiting for them to get old or famous enough to hire for leading roles.

Hearing three good singers at three different stages of their careers was exhilarating, and it even made good vocal and dramatic if not historical sense: Harris/Elizabeth may not have looked like Jarman/Mary’s younger first cousin once removed, but her jealousy of a noticeably pregnant rival (not a plot point, but an incontrovertible fact) who looked as beautiful as she sounded rang true. Both leads are well versed in bel canto style — the opera of early 19th-century Italy — while sounding completely different from each other: Harris clarion and firework-y, Jarman limpid and lighter and a little lower in range. I was particularly taken with Jarman, whom I heard years ago in the summer series Bel Canto at Caramoor and at City Opera; it is a happy thing to get to hear someone who has grown so considerably as an artist.

The men were the weaker link — at least, two of them were. Michael Spyres, the tenor playing the Earl of Leicester, sang at times with considerable beauty. At other times he sounded like he was about to lose his voice altogether — his high notes sometimes paled and faltered, and his Act II duet with Jarman (plot summary: he loves Mary; she loves him; Elizabeth is jealous and has Mary executed) seemed at risk of falling apart in a couple of places. Worse, he often sang with very little expression, sounding as if he were trilling melodies in a drawing room rather than swearing his undying love. And Troy Cook was an anodyne and not very colorful presence as Cecil, one of Elizabeth’s henchmen. By contrast, Patrick Carfizzi, the warm bass who sang the role of Mary’s friend and adviser Talbot, sang with a rich sound and complete emotional involvement, so that his character sprang to life while Spyres’s remained a silhouette.

Antony Walker, the WCO’s stalwart conductor, is another artist who continues to grow steadily over the years. He has always brought energy and verve to the WCO podium, but as his international career develops, his performances seem to take on ever more ease. This one lost none of Walker’s signature crispness, but it also flowed.

A scene from the Washington Concert Opera's production of "Maria Stuarda." (Don Lassell)

Since the WCO routinely offers some of the best opera in town, its fans often ask — during the concert, after the concert, in e-mails once I get home — why it has such a hard time selling tickets. Lisner Auditorium at George Washington University was far from full. You can say that concert opera is a hard sell, but the basic issue is more prosaic: It’s called marketing. It’s no longer enough for a small company like Washington Concert Opera to present excellence and hope people will come. There are professionals who can advise you on how to spread the word, and the Washington Concert Opera needs to hire some, rather than wringing its hands about how hard it is to sell tickets. Here’s an example: The back of the program announced the Washington Concert Opera’s 2013-14 season, with “I Masnadieri” on Sept. 22, and “Il Corsaro” on March 9. Nowhere did it mention the name of both works’ composer. (It’s Giuseppe Verdi.)

And thus ends my public service announcement, apart from letting you know what an enjoyable show it was that so many of you unfortunately missed.