A lot of singers would give their eyeteeth for half the legato Deborah Kieffer seems to find so natural. She sang an extensive program at the National Gallery last night calculated to display this legato to best advantage and to show off many other vocal virtues.

Her way with all five of the languages represented was exemplary, although she was more suggestive in Poulenc's French group, and more poetic in Mahler's German, than she was sultry in the Spanish of the de Falla songs or dramatic in the Italian of Respighi's "Deita Silvane."

She has a big voice, smooth and focused in its lower register but not as reliable up high, capable of conveying a considerable range of emotions and expressions. Had she been willing to take some chances--to bring her pianos down to true pianissimos and to forsake, occasionally, her splendidly produced tone for more dramatic diction and phrasing--there might have been more frequent occasions of stunning communication.

As it was, Poulenc's "Hotel" was enormously evocative, and Mahler's "Lieder eines fahrenden Gesellen" were exceptional, even though some of the top notes missed their marks.

She gave a nice set of five songs by Richard Hoyt a full-bodied reading. They are attractive, lyrical works, with few pretensions, skillfully conceived with fine piano accompaniments. They might have done as well, or better, with a lighter touch, spotlighting the astringency of the texts.

Frank Conlon was at the piano, and, as always, he was the consummate partner, his musical imagination adding immeasurably to the richness of the performance.