E-Mail This Article to a Friend New paths Cecilia Bartoli with the Orchestra of the Age of Enlightenment, the Borromeo Quartet with Richard Stoltzman BY LLOYD SCHWARTZ

It’s hot in here," people at Symphony Hall were saying during the intermission at this year’s FleetBoston Celebrity Series recital by Cecilia Bartoli, the beloved Italian coloratura mezzo-soprano. Two years ago, she caught a cold she attributed to the air-conditioning, and she had to cancel some subsequent concerts. It was certainly warm before she entered. But after she began to sing, things got even hotter.

Bartoli is one of the rare singing stars who keep exploring new material, like forgotten music by Vivaldi and Gluck — the composers of the first two arias on her program. She began with the same Vivaldi aria addressed to Jealousy (from Ottone in villa) with which she began her last Boston recital, the one with the machine-gun trills on the word "inferno" and the change of pace in the middle of the second verse, as she pleads with aching slowness for Jealousy not to kill her. The Gluck was one of her encores last time, a bewitching serenade — "Di questa cetra in seno," from Il Parnaso confuso (she sings it on her Art of Cecilia Bartoli CD) — in which she asks Cupid to hide himself in the lyre of her beating heart as pizzicato strings are plucked under a suave viola melody. Her repetition of the first verse in the most exquisite pianissimo stopped everyone’s breath.

The rest of the concert, except for a Haydn encore, was devoted to her latest area of exploration: the music of Antonio Salieri (in Peter Shaffer’s Amadeus, he’s the hack composer who poisons his arch rival, Mozart). She sang eight of his arias; only two were not on her latest Decca recording, The Salieri Album. But rescuing him from oblivion will probably prove harder than restoring forgotten Vivaldi and Gluck to the repertoire.

Not that Salieri is worthless. On the evidence of the music on this program, he’s an extremely competent musician — he was, after all, a friend and disciple of Gluck and a teacher of Beethoven, Schubert, and Liszt. He composed 39 operas. One of his librettists was Lorenzo da Ponte, Mozart’s greatest librettist. But rather than being an inspired genius, he seems best at working within and manipulating the conventions of his time. Most of the arias Bartoli chose are sung by stereotypes: a jealous wife; a woman looking for the perfect mate or celebrating her own virtue; a victim of cruel fate; a mocker of philosophy.

The most ambitious piece, "Or ei con Ernestina" ("Now he’s with Ernestina"), is a long recitative and aria from La scuola de’ gelosi ("School for the Jealous") sung by a wife who feels her husband has abandoned her. It sounds as if at any moment it might turn into the Countess’s great "Dove sono" from Mozart’s Le nozze di Figaro. It never does. (It was actually written for Nancy Storace, Mozart’s first Susanna.) But it allowed Bartoli a chance to express a range of sincere emotions. All evening, she let the audience take pleasure in the brilliant and shadowy colors of her phenomenal voice and her flawless technique. Without taking a new breath, she could float an endlessly suspended note that then concluded in a spectacular trill. She could breathe life into — or tease vitality out of — music that you might not think twice about listening to from another source. And her face — now playful, now pouting, now tragic — is almost as mobile as her vocal cords.

Salieri is least of all a memorable melodist. Only one aria, "Contro un’ alma sventurata" ("Against an unfortunate soul"), had a piercing tune with a truly seductive contour — in one line ("E calmate, o avverse stelle" — "And calm, you hostile stars"). But there were numerous felicities of orchestration. Bartoli’s accompanist was once again the superb Orchestra of the Age of Enlightenment, directed by violinist Alison Bury. One aria had a florid flute-and-oboe obbligato, and the players (Lisa Beznosiuk and Anthony Robson) joined her front and center. Her final aria, "Non vo’ che già che vi suonino" ("I don’t want anyone playing"), is a comic turn by Lisotta, a peasant girl in La cifra ("The Cipher") who is deciding which instruments she wants — or doesn’t want (bagpipes) — on her wedding day. So individual players also got to shine, demonstrating each example. Every aria ended with Bartoli applauding the players as they applauded her.

The evening began with a Vivaldi C-major concerto. Later, two Salieri overtures and a set of variations gave Bartoli breathing space. The 15 variations on La folia di Spagna (maybe half the number Salieri actually composed) were dazzling inventions on a familiar melancholy dance tune not by Salieri. He didn’t have to invent it. But he added castanets to one variation, a tambourine to another. One combined flute, bassoon, and drum. The orchestra ignited.

The Haydn encore, on a higher level of inspiration, was followed by a charming mocking aria, "La ra la," from Salieri’s La grotta di Trofonio ("Trofonio’s Grotto"). It was late, but no one wanted Bartoli to stop. Next year, maybe her passions will turn to greater music. Maybe she’ll sing more of those slow lyrical arias that break your heart. Still, in any music, it’s thrilling to hear someone so securely positioned at the very height of her considerable powers.