Come September, Bill Evans will have been dead for 21 years. A considerable time - yet in that span, no jazz pianist has come close to replacing him in the popular imagination. Evans is still very much with us: his imprint permeating the world's most popular jazz recording, Miles Davis's Kind of Blue; his stylistic legacy seeping from the work of thriving piano masters Herbie Hancock, Keith Jarrett and Fred Hersch as well as upstarts like Brad Mehldau.

Evans's best playing grips us with its expressive power and keen intelligence. The harmonic imagination, melodic acuity and ultra-sensitive touch cast an inimitable spell. No other jazz keyboardist can pierce the heart with as few notes as Evans, while simultaneously making us ponder how he achieved the effect without excess sentiment or overt emotionality.

It was that kind of singular playing that has created an insatiable desire for more Evans. Fans last year welcomed an 8-disc set of his penultimate live performances, and will no doubt embrace Tenderly: An Informal Session, a fascinating, wholly unexpected recording on which Evans shares leadership with Don Elliott.

Truly an informal session, Tenderly is drawn from musical get-togethers that Evans had with multi-instrumentalist Elliott at the latter's home studio in 1956 and '57. With the host manning the vibraphone (he was also an accomplished brass player) and Evans behind the slightly shopworn studio piano, the two throw around some standards and off-the-cuff blues; Evans also takes a few solo numbers, ranging from ballads to up-tempo bop excursions.

Evans in 1956 and '57 is not Evans in 1959 and '60, the years when all the pieces in the puzzle came together for his playing. If the exquisite touch, chordal ploys and pared-down architecture of his legendary work aren't quite all there yet, much of it is. While Evans's maturity is generally signaled by his joining Davis's unit in 1958, he is still very much his own man at Elliott's. His shrewd accompanying frames the vibist's modest improvisations beautifully, while Evans's own solos have a sense of purpose that exhibit how seriously he took even informal musicmaking. Not surprisingly, given their shared interest in harmonic exploration and subtle interplay, the two mesh together like the old friends they were.

Yet it's Evans's solo performances that offer the richest rewards. Everything Happens to Me, taken in free time, is extraordinary. The unmistakable Evans sound abounds, but it's the palpable sense of exploration that captivates you. Evans moves further and further from any discernible melody and song form as he stakes out daring new harmonies, drawing us into his unique musical universe. His unearthly brilliance probably embarrassed him; abruptly curtailing his melodic reveries on the ballad, Evans quickly says, "Hey, let's watch some TV." They don't make them like William John Evans anymore, and maybe they never will again.