Before reviewing Mosaic’s The Classic Columbia and Okeh Joe Venuti and Eddie Lang Sessions, I have to say one thing: I’ve heard the future of female vocal duos, and its names are Ethel and Dorothea Ponce. Not the least of the pleasures of this bewilderingly heterogeneous eight-CD box set is that it brings to light these obscure early-’30s artists, who, thank God, once did a session with Joe Venuti and Eddie Lang.

On the Ponce Sisters and their original, glassy style, more later. Another duo now concern us. Eddie Lang, generally held to be the first jazz-guitar innovator, and his frequent partner, violinist Joe Venuti, were quite an item in the ’20s and ’30s. "We’d just sit there and knock each other out," Venuti said about playing with Lang. They got on well together because their natures were in conflict. Venuti is a walking party, a center of attention; he carries good times in his violin case. Before he left home, he could already do everything on the fiddle. Now, no song can be a challenge to him. So on "Four String Blues" he sounds like a trolley driver on laughing gas. His Gypsy fiddle is fearsome (the intense "Jig Saw Puzzle Blues"). He can do what violinists are loved for everywhere: turn on the sentiment and keep it flowing through an implied infinity of embellishments ("Dinah," "I’ll Never Be the Same").

Lang is the quiet genius who, by being in the same room, inspires Venuti to subtlety. Lang is by predilection a rhythm player, and his solos have the clarity and delicacy of one familiar with the discipline of supportiveness, of guiding and encouraging, knowing when to intervene, contributing much with little. Venuti bowls you over; you listen to Lang more attentively. More involved with blues than Venuti, Lang is also cooler. A multi-layered guitar solo like the wistful "A Little Love, a Little Kiss" is a stroll through a sonic sculpture garden. On unusual songs like "Perfect" and "Rainbow Dreams," his harmonic intuitions are deeply satisfying; he has an affinity for modulations (which were used more recklessly in popular music then than now).

If there’s a coherence to the box, it’s in the chamber-jazz sound developed by the small groups Venuti and Lang played in (often under Venuti’s nominal leadership). Bass sax and baritone sax, both courtesy of Adrian Rollini (who also dabbles in such instruments as the goofus and the "hot fountain pen"), thicken the textures. Timpani and chimes create an exotic, unsettling mood. Arrangements surprise by their complexity, their range of colors; the musicianship is of a very high order, and devoted to the integration of carefully crafted effects. When the fabric gets turned inside out, the result is the surrealism of "Tempo di Modernage."

Venuti and Lang sometimes backed up tame pop singers, and for every Ethel or Dorothea Ponce or Bing Crosby there was unfortunately a Scrappy Lambert or a Smith Ballew. But since Lang minus Venuti recorded with some of the best blues artists, the Mosaic box has a high blues quotient. Bessie Smith is represented by three of her filthiest lyrics; two other greats, Lonnie Johnson and Texas Alexander, are here, as is the gender-ambiguous Gladys Bentley, a true original. From her to Paul Whiteman is quite a span, but Eddie Lang covered it; from 1926 to 1933 (the period of the box extends to 1935) he and Venuti explored many worlds. To listen to them is to enlarge one’s definition of what jazz is.

Which brings me back to the Ponce Sisters. They contribute five sublime performances to this collection. Beautiful dreamers, they float through every take with discreet melancholy, as if leaning on their elbows and gazing into mirrors. They have a trick of pretending to drift apart only to rejoin in two-part harmony; one wonders whether they liked each other. Along with their maddeningly perfect diction, they have the gift of total detachment. The excitement of their accompanists fails either to faze or to rouse them. It might be stretching things to call the Ponce Sisters "jazz," but they do swing — especially on the reproachful "So At Last It’s Come to This." Are they white-hot mamas posing as Ohio schoolteachers or vice versa? Their note bending ("a million ti-imes a da-ay" on the contemplative "A Million Dreams") enhances their carefree mystique while hinting at sybarite sophistication. When do we get the Ponce Sisters box set?

The Classic Columbia and Okeh Joe Venuti and Eddie Lang Sessions is available only through Mosaic Records. Write to Mosaic at 35 Melrose Place, Stamford, Connecticut 06902, or call (203) 327-7111, or go to www.mosaicrecords.com.