It was 20 minutes for Mozart and an hour for Mahler last night as Coling Davis led the visiting Boston Symphony Orchestra in the former's Symphone No. 34, and the orchestral song cycle, "Des Knaben Wunderhorn," by the latter.

Jessye Norman and John Shirley-Quirk were the Mahler soloists, as they have been on recordings. Each artist fully understands the humors of the songs, the biting wit, the earthy colors and the human sorrows. Norman sang in a wide range of shades, her voice at its loveliest.

Shirley-Quirk is a marvelous interpreter of these songs, requiring of his voice that it produce every nuance of meaning, even though the vocal resources are, at times, not enough at the top and bottom, while the singing method reduces a resonance that would be welcome.

Interpretively, however, these songs are not likely to be better presented these days than they were under Davis' sensitive, skilled direction. He elicited sounds from the great orchestra, as in the dialogue between the prisoner and the girl, that were, by turns, of radiant beauty, or of stinging sarcasm.

The essential rubatos were ideally handled, giving each soloist the sense of freedom against Mahler's large canvas.

Davis also conducted a Mozart symphony that opened in fine, ceremonial breadth and proceeded at every point thereafter in excellent style. Among its special pleasures was the superb vitality of the violins in some of Mozart's most exciting allegros.