Okay, now I’m really confused. Sunday afternoon at Alice Tully Hall was supposed to be the Paris concert in the Mostly Mozart series “Traveling With Mozart.” Now, bearing in mind that there is also going to be an Italy installment, why was the major work on the program the Handel cantata “Da quel giorno fatale,” more popularly known as “Il delirio amoroso”? The work was premiered in Italy in 1707 while Handel lived in Rome and worked with violinist and ensemble leader Arcangelo Corelli and famous castrati like Senesino.

The answer apparently is that the performers were French, the period instrument group Concert d’Astree, the soprano Magali Leger, and the conductor and harpsichordist Emmanuelle Haim. When Joshua Bell performs next week, will there be pieces that Mozart heard on his trip to Indiana?

Ms. Leger studied with one of my favorite singers, Christiane Eda-Pierre from Martinique. She sports a similar voice, light and innocent in the upper register but dark and hefty in the lower. This type of versatility served her in good stead for the demanding arias of Handel, and she showed a depth of understanding of Baroque ornamentation that was most impressive. Especially in the aria “Un pensiero voli in ciel,” Ms. Leger was wonderfully adept at feathery filigree, and little crescendi interspersed in the lyrical line.

But most astounding was this artist’s ability to sustain a slow, measured crescendo for a very long time without breathing. Starting extremely softly, she was able to reach a solid forte over time with no loss of intonation. She also intelligently employed the intake of breath to elongate her line by singing through her inhalation. Remember this name: Magali Leger. In her arcane world, she may become the next Cecilia Bartoli.

There was indeed French music on the program as well, the suites to the two pivotal operas in the career of Jean-Philippe Rameau. Not satisfied to be a great theorist and proficient organist, Rameau attempted to storm the battlements of the Paris Opera with a work whose libretto was written by no less a figure than Voltaire, but the plot of Samson being biblical, it was rejected. Rameau submitted instead “Hippolyte et Aricie,” only to have it panned by critics and public alike. Discouraged almost to the point of capitulation, he soon re grouped and composed a brighter and more potentially popular hybrid combining elements of opera and ballet. “Les Indes Galantes” was a smash hit and sent Rameau off on a 30-year journey of accolades and fame.

Immediately in “Hippolyte et Aricie,” you can hear the progressive elements that rankled the critical establishment, the same sorts of innovations that would be objectionable to Wagner’s detractors more than a century later. The harmonies are daring for their time, the instrumentation raucous, the discords proudly displayed. In the hands of the excellent Concert d’Astree and their highly proficient conductor, Rameau’s tableaux were extremely inventive and surprisingly colorful.

Using period instruments allowed for a sense of the exotic. Wooden flutes and recorders, for example, sound completely different than metal or plastic instruments with the Boehm key system in place. When the flutist – or, since this is early music that we are discussing, flautist – blew into a mouthpiece to simulate the wind, we knew that we were experiencing something not of the present time and place.

Also evoking the raw power of the period were the variety of instruments manned by the one percussionist. Little baby timpani, tuned to a high, taut pitch; a thundersheet; tambourine; triangle; and a side drum straight out of a Delacroix historical painting set a Janissary mood. The conductor, Ms. Haim, reveled in this discordant cacophony that complemented the grouping of like instruments together in spots, evocative of a medieval consort.

With all of the emphasis on authenticity, it was a bit odd to see the maestra gesturing in a contemporary manner. You would think that, since the invention of the steel-toed shoe, she might instead beat time with a stick like Jean-Baptiste Lully. She did, however, occasionally punctuate her conducting with ticklings of her harpsichord, taking a supporting role to regular Astree keyboardist Laurent Stewart.

Ms. Leger was also on hand for these suites and dazzled with the lovely “Viens, Hymen” from “Les Indes Galantes” in an ethereal singing contest with the flute. Later, her “Papillon inconstant” was a primer on ornamentation. As a whole, this concert contained some of the freshest sounds heard in New York for quite some time, so old that they were new again.

The Mostly Mozart Festival thus far has been one sellout after another, and so it was a bit surprising that this Sunday event had more than a smattering of empty seats. There is, however, an explanation. Originally, Lorraine Hunt Lieberson was to have premiered the Peter Sellars stagings of Bach cantatas at the Rose Theater this same afternoon. Many people were extremely disappointed when she canceled, but by then the thought of substituting another concert might have been far from their mind. Had Ms. Lieberson actually performed, many – including me – would have missed Le Concert d’Astree.