More than a box set, Vladimir Horowitz: The Unreleased Live Recordings 1966-1983 is closer to being its own musical planet, full of familiar yet strange creatures who adhere to no laws but their own. Of course, there's really only one creature, pianist Horowitz, a musician who truly lived up to the word legendary, though not necessarily because he was infallibly great.

The 50-CD set ($149.52 on Amazon), originally recorded by Columbia (now Sony) and RCA, comes from a time when recording machines were ever-present at the live concerts he gave, recordings that were distilled down to an LP or two a year, with the rest left unheard by the public. Now, like Deadheads, we can follow Horowitz through 26 concerts, sometimes playing almost the same repertoire twice in consecutive weeks.

The significant difference is that the Grateful Dead were constantly improvising; Horowitz enjoyed great interpretive freedom, but within the framework of a central interpretive conception that tended to stay the same from one performance to the next.

Coincidentally, Deutsche Grammophon has come out with Vladimir Horowitz: Return to Chicago ($19.69 on Amazon), a 1986 live recording that was broadcast once and then rediscovered two years ago, documenting the pianist's final period, three years before his death at 86. The two-disc Chicago set is a must-have for anyone with an even casual admiration for Horowitz.

Though often described as a charismatic throwback to the big-ego personalities of the early 20th century, he was a unique figure whose roots lay in Imperial Russia, but who stood outside any school of performance. And this Chicago set represents the summation of that, though in repertoire within reach of his aging hands. Bonus cuts include two rare radio interviews revealing his sense of humor and penetrating observations - surprising for a musician whose brains were assumed to be in his fingers.

Some say the 66-year span of Horowitz's career had a long artistic evolution. Others argue that he never really changed, but appeared periodically, like a comet, dazzling beholders among his periodic years-long retirements. Almost anything ever said about his playing - great, awful, contradictory - finds verification somewhere in these sets.

Those who dismissed him as a musical "embalmer" will zero in on his cool, well-buffed exteriors. But you'd never say that about his 1968 Boston concert played days after the death of the Rev. Dr. Martin Luther King Jr., whom he greatly admired. Comparing the two May 1980 concerts at Lincoln Center, you can forever argue with yourself over which version of Liszt's Consolation No. 3 is the more beautiful. Do we need both? Why not? They're both here.

All the while, he asked for - and got - performing conditions that turned all neutral factors of any concert situation in his favor. He played mostly recitals, and on Sunday afternoons with his own piano, sometimes hoisted by crane from his New York City townhouse. Also, the piano was doctored so much to his own specifications, with a light, ultra-responsive action, that the instrument sometimes doesn't even sound like a piano, but some hybrid instrument from, well, Planet Horowitz. His programs seem old-fashioned, sometimes with a lot of smallish and miniature works.

Complete sets of pieces - whether Debussy preludes or Chopin ballads - were never for him. Quirks include his affection for little-known Clementi sonatas; maybe one movement is worth hearing. Schumann's Piano Sonata No. 3 isn't a great piece, and it comes out so Horowitzized that the pianist is basically a co-composer.

Liszt's great Sonata in B minor is a seething mass of Horowitziana, full of extremes in tempo and volume that perhaps only he could think of and only he could actually do. He could have gone to town on Schumann's Kreisleriana at Philadelphia's Academy of Music in 1968, but he instead probed the piece like a psychoanalyst. You wish his programing were a bit more serious. Beethoven's Piano Sonata No. 28 Op. 101 comes off beautifully. Why not more of that?

Again, it's Planet Horowitz. And his mechanism must have been delicate. The few times one can hear Horowitz playing the same program on consecutive Sundays, the second one tends to be a distant second. Don't expect a musical diary, because, in contrast to his contemporary Arthur Rubinstein, Horowitz's long-term interpretive journey wasn't linear nor his greatness consistent. The delicate colors he drew from his piano one minute could turn to fortissimo mud the next.

Most dramatic are his 1983 concerts when his fingers weren't cooperating, no matter how much his interpretive conceptions tried to fight their way out. Though Horowitz's retirement from 1953-1965 was about mental illness, this was the first time he fell into a different kind of inner distress; he blithely frequented gay bars in the 1970s but couldn't handle being outed in the 1983 Glenn Plaskin Biography of Vladimir Horowitz. Reportedly, he was "overmedicated." Again, he retired.

Some Horowitz-philes feel these 1983 recordings shouldn't have been released. To the set's credit, his disasters in Tokyo (they were recorded and described by his wife, Wanda, as "a funeral") are not issued here. That's why the separate appearance of the Chicago concert is so serendipitous. His resurrection was a bit rocky until he found his legs as a born-again Mozartean, employing his filigree sense of line more expressively than ever. The Scarlatti Sonata in E major K. 380 that opens the Chicago disc, full of tiny tempo variations that turn the music into something beyond itself, is a three-dimensional entity that dialogues with your own humanity. Thus, Horowitz's recordings can be so many things to so many people, there may never be any consensus on who he really was.