There is, at times, an unusual blend of the ethereal and the earthy in Judy Collins's singing that gives some of her songs a particularly distinctive quality.

In a concert a Carnegie Hall Saturday night, an annual Christmas appearance for Miss Collins, she ranged from traditional folk song to Jacques Brel with sampling en route of her own work and of the compositions of Bob Dylan, Leonard Cohen, Gordon Lightfoot and Joni Mitchell. The concert was repeated last night.

It was a varied repertory, done sometimes with folk-derived backing, sometimes with a rock beat, sometimes with gospel enthusiasm. But no matter what the song or what the style; the sparks were raised when the ethereal rubbed against the earthy. At other times Miss Collins tended toward a bland approach, which emphasized the essential similarity of a great many of her tunes.

And when she moved to a distinctly different type of song - a medley from "Jacques Brel Is Alive and Well and Living in Paris," "the Desperate Ones" and "Sons of ..." - this blandness produced a rather austere feeling in songs that usually can scarcely help being projected with a burning intensity.

The audience that filled the hall was particularly responsive to a medley of Joni Mitchell's songs and a highly effective pairing of Leonard Cohen's "That's No Way to Say Goodby" and "Sisters of Mercy." Miss Collins accompanied herself on guitar and piano and was supported by a trio led by Gene Taylor, bass, with Richard Bell on piano and Susan Evans on drums.