It looks like a boxed set of four CDs and a booklet. But it's not. It's a treasure chest.

"Louis Armstrong: Portrait of the Artist as a Young Man, 1923-1934" is a collection of some of the most astonishing, engrossing, thrilling and beautiful performances in jazz. Not just the best in early jazz, but the best in jazz, period.The set traces Armstrong's recorded artistry from his first discs in April 1923 through October 1934. Altogether, 81 pieces are gathered, showing the increasing power of this genius of cornet, trumpet and voice.

Armstrong continued to perform for decades after 1934, but in a way that year marked the end of an era. He returned from Europe and stopped recording for six months the next year, then resumed with a somewhat different style. So this was as good a point as any to end the set; anyway, it just may wind up as the first volume of a larger retrospective.

Overall impressions: Digitizing the ancient records has wiped out the hiss, woofing and crackle that ordinarily interfere with our appreciation of 78-rpm records. With only a few exceptions, the sound quality of these cuts is exceptional. Armstrong's soaring trumpet and raspy voice come alive in your ears.

That's not to say that he is the only jewel in the diadem. On these cuts he plays with many of the greatest musicians and (to a much lesser extent) singers of the period, from Earl "Fatha" Hines to the Dodds brothers, from the Dorseys to Bessie Smith, Lil Hardin Armstrong, Lionel Hampton and Sidney Brecht.

The first recordings are made with Joe Oliver - the band leader who gave Armstrong his big break, inviting him to travel from New Orleans to join his King Oliver's Creole Jazz Band in Chicago. Lil Hardin's piano playing is delicate, and Armstrong and Oliver's cornets are so much in sync that at times I cannot tell them apart.

But they are still deeply immersed in the Dixieland tradition.

Contrast the relative lack of sophistication and the standard style of Oliver's band with the last cut, "Song of the Vipers," a mysterious piece by Louis Armstrong and his Orchestra, with its odd meditations and changes. Armstrong preaches a peaceful trumpet sermon, veering into memory and the heavens.

In the 11 years between those cuts, Armstrong defined jazz. And from his scat singing to the intricate and amazing solos, it's all here.

So many magnificent performances are gathered in the set that it's hard to single out particular ones. I found myself saying, "Boy, they're good," while listening to "Beau Koo Jack," a fast piece from 1928.

In the 1929 arrangement of "I Can't Give You Anything But Love," the Armstrong Orchestra breaks new ground. It starts with a schmaltzy approach, but then the leader takes over, playing and singing beautifully.

He scat-sings an astounding chorus that includes, "Gee! I'd like to! See Ya! Loookinn' swell!" and a little later follows up with the same riff on the trumpet.

The first take of "Stardust" (of two versions presented here) is a gorgeous cover of the Hoagy Carmichael standard. Armstrong sings, at one time repeating the heartfelt "Oh memory, oh memory, oh memory." The orchestra provides a wonderful, plowing backup to Armstrong's pure, soaring trumpet.

Many don't sound a bit dated. But occasionally an inept singer or goofy arrangement mars one's appreciation.

A perfect example is "Tight Like This," by Louis Armstrong and His Hot Five, 1928. It is vaudeville in some places, with silly dialogue exchanges. But the music itself drills right into the heart of jazz, with Hines' shifts in tempo and Armstrong's stunning solos.

Of the whole boxed set, my favorite is "Sugar Foot Stomp," in which Armstrong leads the Fletcher Henderson Orchestra into the world of swing.

I admit I'm prejudiced in its favor because I happened to buy an original 1925 record of this one for 10 or 20 cents in a junk store on the Eastern Shore of Maryland, around 1969. But it's still a masterpiece.

In addition to the superlative music, the set comes with a 78-page booklet. This is a fine short biography, an elucidation of the man's life and his music, with discussions of the recordings on the CDs.