Columbia/Legacy C4K 57176 (four CDs) .

A definitive collection of the greatest of all jazz musicians during his pathbreaking years: What more could you ask for? You could ask for notes that provide a closely observant, illuminating, entertaining guide to the eighty-one tracks, an expert lesson in their wonders, and that is what you get here, from the jazz scholar Dan Morgenstern and the saxophonist Loren Schoenberg. For instance, in “Big Butter and Egg Man,” Armstrong’s vocal “gives us a taste of his comédie acting of the day, in rather broad strokes. . . . But then, in one of those miraculous shifts of sensibility, he constructs a cornet chorus that is sublime, from the initial triple call through the supremely relaxed reinvention of the melody. (You can almost sense that young Lester Young . . . was hip to this solo.)” “Too Busy,” from 1928, “features one of the more inexplicable phenomena in the annals of recorded jazz, a singer who seems to have no talent whatsoever, yet is surrounded by some of the greatest musicians of all time. . . . The highlight: when [she] returns, Louis joins her in a vocal duet, scatting behind her imperturbably corny singing. It is a rare moment, and if anyone needs a definition of swing and the lack thereof, this is made to order.” If you love jazz at all or even are just curious, don’t miss this important exploration of one of its pinnacles.