Soprano Nadine Sierra. (Merri Cyr)

One of the pleasures of a vocal recital is hearing the way the instrument changes and develops as it warms up. A piano’s timbre stays basically the same, but the voice that sings the first song on a program is not the same voice you hear after an hour of singing.

Nadine Sierra, a lovely 27-year-old soprano, demonstrated this during a recital in the Shenson concert series at the National Museum of Women in the Arts on Wednesday that was polished throughout but that deepened considerably over the course of the evening. In her first songs, two Schubert rarities called “Florio” and “Delphine” (from the play “Lacrimas”), she showed a startlingly warm and mature-sounding, almost mezzo-ish middle voice and a smaller, clean and pretty top.

As the first set continued with, first, Mozart’s “Ruhe sanft” and then Debussy’s “Quatre chansons de jeunesse,” the top took on an air of slight stridency as she put pressure on it to match the middle (with French seeming a slightly more comfortable fit than German). By Strauss’s four “Mädchenblumen,” she had a slightly metallic, brassy sound that she wielded with careful calculation, although her coloratura throughout was ever so slightly sloppy. Kamal Khan, the pianist, offered clear and expressive accompaniment with, also, a couple of minor slips.

After intermission, a set of three songs by Joaquín Turina, “Homenage a Lope de Vega,” seemed a perfect fit for her voice, allowing the metallic quality to bloom and letting the warmth in the middle voice creep into the top.

But as she moved into her final set, a medley of lighter and more stage-based works — “Einer wird kommen” from Lehár’s “Der Zarewitsch”; a number from Messager’s “Madame Chrysanthème”; the aria “Me llaman la primorosa” from the zarzuela “El Barbero de Sevilla” — her voice began to take on the kind of exquisite silvery evenness and floating quality one might expect from a young light-lyric soprano. Stephen Foster’s “Beautiful Dreamer” was simply ravishing, and Ricky Ian Gordon’s “Will There Really Be a Morning?” had a lot of the expressivity that the more calculated songs on the program’s first half had lacked.

And if it weren’t already clear, the encore, “O mio babbino caro” from Puccini’s “Gianni Schicchi,” with its radiant, floating notes, showed the voice in full flower and underlined the point of the evening’s story: Nadine Sierra is a natural opera singer who is still finding her way in the art-song literature. It should be fun to watch her continue to develop.