Turning from the Mozart and Mahler that filled its subscription concerts this week, last night in National Symphony Orchestra played another of its popular Encore Series, with Andre Kostelanetz conducting and Anna Moffo as soloist.

Out of his vast repertoire and experience, Kostelanetz brought his enthusiastic audience several things that are too rarely heard, whether on Pops or on the sometimes heavier subscription programs. For instance, the "Enchanted Lake" by Liadov is a poetic gem that can stand on any orchestral program and not feel inferior. It was played last night with a silken beauty from the strings and a hushed quality in the woodwinds that for a few moments held time captive.

Equally affecting in a different vein was the intermazzo from Puccini's "Manon Liscaut." Again the playing had a wonderful touch that turned its open simplicity into a very special matter. These lovely short pieces raise good questions about why they do not come along regularly.

Moffo, looking gorgeous, sand Lauretta's "O mio babbino caro" from Puccini's "Glanna Schicchi" in a way that would melt the heart of any girl's old daddy. With a marked shift in style, she then moved into Elvira's "Ernani, involami," from the Verdi opera. For this she had all the agility she needed, combined with her expert sense of style.

Later in the evening, when Moffo added "Chacun le sait" from Donizetti's "Daughter of the Regiment" for an encore, it was interesting to compare her high C with those in the Verdi aria.

Those in the Donizetti were squarely on the mark, brilliant in texture, and dramatic in impact. As for Moffo in the two big arias from "Adriana Lecouvreur," this is a matter of an ideal voice and temperament being placed entirely at the disposition of music and text. In the second, especially, Moffo easily won the encore she soon sang.

To all this Kostelanetz added a sturdy trio of big moments from "Petrouchka," scenes from "The Seasons" by Glazunov, and Rossini's "Willliam Tell" Overture.