It was Diva Day at Symphony Hall on Sunday, actually a Two Divas-Four Dresses affair: a charming celebration of friendship and collegiality between two superstars who both won Met auditions 25 years ago this month, and who have been friends ever since— as if you didn’t know, Renée Fleming and Susan Graham.

Fleming’s phenomenally extensive musical biography (she has sung 54 opera roles and is, according to her PR, “the people’s diva“) almost pales in comparison to her extra-curricular fun facts. She has been an “ambassador for Rolex timepieces” since 2001, and has a fragrance, “La Voce,” designed for her (proceeds go to the Metropolitan Opera). Master Chef Daniel Boulud created a dessert, “la Diva Renée,” in her honor, and there is a Renée Fleming iris. The most famed designers vie to outfit her, and in “Prairie Home Companion” she has appeared as “Renata Flambé.” She is the first woman in the Met’s history to have Opening Night to herself. I was also very happy to have witnessed Fleming in action in her fascinating and, especially for singers, extremely informative master class at Sanders Theatre on Saturday morning. No diva behavior, just a fun and very funny person who wished she had had more caffeine before showing up in front of a thousand fans.

Sunday was the sixth and last stop on the Fleming-Graham road show, and both seemed utterly comfortable in their program of French art songs and arias, Graham’s specialty. (Fleming, admired for her Strauss heroines, admitted she loved singing in French best, and that her “favorite singer of French music is Susan”). The pianist, Bradley Moore, was superb, one of those amazing vocal partners not terribly well-known, although he is assistant conductor at the Met. My only regret is that for a French solo, he chose Debussy’s overplayed “Clair de Lune.” from Suite Bergamasque. People at intermission seemed much happier than I with this choice.

The stage was set to resemble an intimate 19^th-century salon with four large potted plants, two stuffed chairs, two reddish wood music stands as well as the piano, and throughout the concert, there was the kind of chatty banter one hears on “Live from Lincoln Center” (which Fleming frequently has hosted) or backstage at the Met during intermission interviews (both women are very good at this). While it was informative, it was also miked and began to feel intrusive and mood-breaking. The two singers were trying to create the charming, intimate ambiance of a salon, but Symphony Hall doesn’t really lend itself to this without a serious suspension of disbelief.

The program was generally taken from the Belle Époque (1871-1914), opening with three light mélodies by Saint Saëns. Four Fauré songs followed, beginning with the beautiful “Puisqu’ici bas toute âme” (As each soul here below, text by Victor Hugo) followed by the deeply calming “Pleurs d’or (Tears of Gold, text by Albert Victor Samain). The biggest surprise for this listener was the famous “Pavane” (text by Robert, comte de Montesquiou-Fezenac) which had a emotionally wrought text, Graham and Fleming standing with crossed arms. The most fun piece was “Tarentelle” (text Marc Monnier) with which the singers had a ball.

For her solo turn, Fleming chose two gorgeous pieces by Debussy, “Mandoline” (text by Paul Verlaine) and the bittersweet “Beau soir” (text by Paul Bourget).  In Léo Delibes’ “Les filles de Cadix” (The Girls of Cadiz text by Alfred de Musset) Fleming seemed to be really enjoying being a coquette (one with a dazzling vocal technique!).

The hoped-for intimacy of a Parisian salon occurred after intermission when Graham, resembling a statuesque goddess in a shimmering silver one-shoulder gown, devoted herself to four songs by a composer she has championed, Reynaldo Hahn. The gown was just the beginning; Her voice completely beguiled, seduced, and thrilled. Many who had heard Renée Fleming live, at Tanglewood or at Symphony Hall, had never heard Susan Graham, who is much better known to, say, New Yorkers who know about her triumphs at the Met, most recently in Berlioz’s Les Troyens. I loved Hahn’s “Printemps” (Spring, text by Théodore de Banville) and ordered a copy of her CD of Reynaldo Hahn as soon as I got home.

The two friends teamed up for Berlioz’s devastating “La mort d’ Ophélie.” Has bad news ever been delivered this ravishingly? The end of the song has poor Ophelia drowning in a deep abyss, “stopping her barely begun melodious song.” In a concert with so many high points, this was surely one of the most sublime. A spirited song by André Messager about Blanche-Marie and her sister Marie-Blanche who imagined themselves twins had the divas locking arms, after which the very famous “Barcarolle” from The Tales of Hoffman by Offenbach received a beautiful performance. What was most striking besides the easy rapport between the women was how uncannily their voices melted into each other. They were clearly meant to sing together, and it was a great joy to witness.

The last scheduled number was perhaps the best—this is saying a lot—the ravishing “Duo des fleurs” (Flower Duet) from Lakmé, appropriated by British Air. The audience went wild; the singers and pianist obliged with a duet, “A, guarda sorella,” from Mozart’s Cosi fan Tutte. Fleming marveled at how this is the first time the two had ever sung together as two women; Graham had always had the pants role.

Graham sashayed out with a cigarette hanging from her lips (this is what Reynaldo Hahn did), sat down at the piano and tossed its music onto the floor. She then accompanied herself in “La Vie en Rose,” Édith Piaf’s famed torch song. She exited in character. The audience loved her. It was something I will never forget; many in the audience had tears in their eyes. Fleming, in a stunning red gown, sang one of Cantaloube’s Chants d‘Auvergne  and finally the two sang “Evening Prayer” from Hansel and Gretel with heartbreaking simplicity and unadorned beauty. What a stunning way to celebrate 25 years of friendship.

There were also moments when Graham let her inner Texan out and was just hilarious.  Perhaps they thought chatting would humanize the usual Diva Mystique, but their singing did that in spades.

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