When two established soloists get together on the bandstand in the congenial atmosphere of a cozy jazz haunt, one waits for the sparks to fly. Indeed they did last night in the One Step Down as trombonist Slide Hampton and tenorist Frank Foster carried off a stem-winding opening set of three half-hour pieces that had one asking, "Don't these guys ever let up?"

The southpaw bone player, one-time Lionel Hampton (no relation) sideman, pulled out every known sliphorn device and then a few more on Thelonious Monk's "Straight, No Chaser." Wickedly fast staccato, facile transitions so silken smooth legato, gruff vibrato, comic slide effects, all falling neatly into place as a spur-of-the-moment compositional gem.

Former Basie-ite Foster is an improviser with a seemingly bottomless well of inspiration. He whipped up Clifford Brown's "Joy Spring" to the top of his horn and descended as quickly, with quotes flying to the winds, including a fragmentary Scottish reel. Switching to soprano sax for Kenny Dorham's "Blue Bossa, his tone became Eastern with swirls and a raga-like intensity.

It takes a combustible rhythm team to fire such an engine as this pair and locals Reuben Brown on piano, Steve Novosel, bass, and drummer Keith Killgo proved up to it.

The quintet plays again tonight.