RON CARTER and Cecil McBee enjoy a luxury afforded too few jazz bassists: the opportunity to record under their own names. It's not that the bass, once strictly relegated to playing a harmonic role in jazz, hasn't enjoyed greater exposure and prominence since Jimmy Blanton's innovations were first showcased by Duke Ellington more than 40 years ago; it clearly has. But while bassists continue to grow in number, skill and stature, there still is a reluctance to record the instrument as a lead voice in jazz.

Carter, of course, is the exception to the rule. Since leaving the Miles Davis Quintet in the late '60s, he has recorded in a variety of imaginative and distinctive settings, playing not only the double bass but also, more recently, the higher-pitched piccolo bass as well. Oddly enough, despite this diversity of instrumentation, he never has recorded an album of his own without benefit of piano. Until now, that is.

Carter's latest album, "Etudes" (Elektra/Musician 60214-1), reunites the bassist with two alumni of Davis groups: trumpeter Art Farmer and drummer Tony Williams. Completing the group is the young tenor-saxophonist Bill Evans, who currently is a member of Davis' band. Among other things, this pianoless quartet allows for greater interplay between bass and drums, something that is immediately evident on the slower, more introspective selections. When forward thrust is called for, the combination of brass and reeds supplies the color and momentum Carter's music previously derived from pianists such as Kenny Barron and Herbie Hancock.

The music on "Etudes" is of differing moods, shifting between the jaunty, boppish flavor of "Last Resort" and "Arboretum," where the horns play a prominent role, to "Bottoms Up" and "Doctor's Row," where ruminative exchanges between the bass and drums develop fully.

Evans and Farmer turn out to be surprisingly compatible partners. They consistently display different yet complementary styles: Farmer the perennial romantic possessing a softly glowing tone; Evans headstrong and assertive. When Carter yields to them, his playing often takes on the form of walking, skipping, stuttering bass lines, big toned glisses, bubbling ostinatos or sly, understated embellishments. When he and Williams return to the spotlight, sharp dialogue develops quickly. On "Bottoms Up" the two are particularly expressive, with Carter alternating dark and probing lines with a momentary glimpse of boogie woogie, while Williams responds with fluttering brushes and telling accents.

Four of the six compositions included on "Etudes" are Carter originals, and they include many moments of low-keyed virtuosity. But they are by no means unique in that regard. Another Carter album--the recently released "Parfait" (Milestone M9107), featuring Carter on piccolo bass backed by pianist Ted Lo, double-bassist Leon Maleson and drummer Wilby Fletcher--is graced by a pair of superb homages to the late composers Thelonious Monk and Duke Pearson.

Although it's not always easy to tell where the piccolo bass leaves off and the double bass begins, the two instruments make for a sublime blend, creating intricate textures that make Monk's "Round Midnight" all the more haunting. "Blues for D.P.," on the other hand, starts out as a common blues but builds steadily and ultimately captures a measure of the beauty and lyricism of Pearson's own writing. The album's other highlight is "New Waltz," a Carter original that unfolds at an elegant and stately pace. Both albums beautifully display the subtler side of jazz expression.

Cecil McBee hasn't recorded anywhere near as often as Carter, but he has a habit of making every album count. "Flying Out" (India Navigation IN10053) is his latest, and as the title suggests, his most adventurous, with an emphasis on striking string ensemble performances played by McBee, cellist David Eyges and violinist John Blake. The music, much of it passionate, incorporates classical references, abrupt twists and occasionally the streaking color of Olu Dara's cornet. But mostly it is the sharp improvisations and the nimble alliance forged by the string players, subtly propelled en mass by drummer Billy Hart, that hold one's attention.

McBee's distinctly confident tone is especially enjoyable on this recording: no matter what the mood--unobstructed swing, earthy blues, imaginative string trios--his tone is full, his phrasing precise. An unexpected delight is the lovely ballad "Truth--A Path to Peace," which finds McBee on piano, outlining the melody in a darkly romantic manner. It's but one example of the thoughtful and provocative music heard on "Flying Out."