LINDA RONSTADT has always had a sexy, kittenish quality in both looks and performance, and I've had a little crush on her and her sound since her early days with the Stone Poneys. Well, kitty's all grown up now, and Capitol's new "Linda Ronstadt" is not only the finest thing that she has yet done interpretively, but reveals that she's developed a rich and warm voice that can soar or whisper without ever losing its consistently appealing loveliness. Not since Joan Baez can I remember a folk-inflected female singer who communicates so affectingly. And, as much as I admire Miss Baez, there are times when a certain Dresden-china look-but-don't-touch quality creeps into her work. But Ronstadt always seems touchable, and eminently touching, in all her material.

Superficially, this album can be classified as country, in perhaps the same way as those of Kristofferson. But within that chosen style glow Ronstadt's intelligent sensibility and joyous musicianship. They permeate such things as her own arrangement of the Guthrie-Ledbetter-Lomax Ramblin' Round; she sings that aching, wistful song in such a rhapsodic and pulsating voice that it transcends categories. And there is Rescue Me, whose gospel style is only a frame for a spectacularly involving performance. I Fall to Pieces was recorded at the Troubadour in Los Angeles, and in many ways it is the best thing in the album, for you hear the mounting excitement of an artist responding to a responsive audience and effortlessly producing a galvanizing performance. Although the tracks were recorded in several locations, the album as a whole is no hodge-podge of varying moods; instead, it has the nitty-gritty feel that comes of the successful search for the perfect setting for each song.