Gustav Mahler's "Kindertotenlieder" is, as its German title indicates, a cycle of songs about the death of children. Perhaps that is why we don't hear it performed more often and why it was so special to hear it sung--beautifully--Sunday night at the National Gallery.

Children do not die (of such diseases as cholera, whooping cough and scarlet fever) as often as they did in the early 1900s, when this music was written. And there are more cheerful subjects to sing about, even in the music of Mahler, who tends to be rather gloomy.

Another reason for the rarity of performances is that these songs are composed for an alto. This kind of voice has become rare among female soloists in the last generation or two, while the countertenor, with roughly the same range, has become common among men, particularly in early music. Alto is the lowest recognized category of women's voices, though you occasionally see a chorus today that has a woman among the tenors. There are also choruses with men singing among the altos; we aren't quite as rigid about such things as we used to be.

Vocal categories are not entirely arbitrary; some voices are naturally higher or lower than others. But for some singers (for example, Placido Domingo, who began his career as a baritone), becoming a tenor or baritone, a soprano or mezzo, is a matter of personal choice--which part of your vocal capabilities you exercise and develop, which part you neglect.

In our time, most singers have chosen to push their voices upward (sometimes shortening their careers by going too far), because high notes are considered more glamorous than low notes. The result has been a decline in the number of female alto soloists, while the male alto supply has grown both in quantity and in quality.

The alto voice is the one that opera composers have traditionally assigned to mothers, a fact that makes it especially appropriate for a cycle of songs about children. It is a voice particularly at home with feelings of gentle unhappiness (we seem instinctively to associate high notes with joie de vivre and low notes with lamentation), but it is also a voice particularly suited to giving consolation.

All these points were clearly relevant in Beverly Benso's interpretation of the "Kindertotenlieder," Sunday night with George Manos conducting the National Gallery orchestra.

Benso is a true alto, with the tonal richness and emotional warmth that have made this vocal range a special pleasure to connoisseurs. There is a fine array of color nuances, vocal and instrumental, in Mahler's special brand of gloom, and it brought out the best in the singer and orchestra, including individual orchestra members who had occasional solo moments.

The five poems of this cycle are full of sensory images--sunrise and shadows, "dark flames," mists and tempests, stars and tiny footsteps--that were translated into music in this performance, particularly in the final song, whose transition from stormy, dramatic intensity to tranquil resignation sums up the cycle.

On either side of Mahler's journey through darkness, the program put some of the brightest and most bubbly music an orchestra can play. The evening opened with Mozart's "Marriage of Figaro" overture and concluded with Mendelssohn's "Italian" symphony, both performed with a vigor that stirred the National Gallery's legendary reverberations.

Manos conducted with crisp phrasing and careful dynamic control. The acoustics favored bass lines, at least from where I was sitting, and balance and intonation were not always perfect, but the music was invigorating.

Free National Gallery concerts in December will feature soprano Carmen Balthrop Sunday, violinist James Buswell on Dec. 12, the Washington Men's Camerata on Dec. 19 and pianist Jeni Slotchiver on Dec. 26.