Miles Davis was not the only major figure in American music who was a restless spirit. Among his heroes were Louis Armstrong, Frank Sinatra, and Duke Ellington – who also consistently evolved from one type of music to another over the course of multigenerational careers. But only Davis incorporated change into the core of his artistic personality. In Davis’s career, change is the only constant.

There were times when Davis seems to have changed just for the sake of change, and other occasions when the changes were apparently occasioned by factors other than an exclusively artistic decision – such as his move into electric and rock-inspired music at the start of 1970s. But for the most part, he just never stopped working, never stopped collaborating, and never stopped listening.

The breadth and diversity of his career is thoroughly documented in Sony Legacy’s ongoing series of super-sized Miles Davis boxes (AC7K 90840-L1), whose seven boxes must contain more than 60 hours of music by now. The latest installment is dedicated to the period between the great player’s two most famous ensembles, those of the late 1950s and early 1960s, and it shows him looking for – and finding – the right sound to take his career forward.

“You know, one thing I like more than anything else is playing ballads,” Miles Davis once told his sideman, the late Bob Berg, “which is why I can’t play them anymore.” Davis was above all a highly sensitive man, and often a very frail and sickly one, prone to illness – especially if you regard drug addiction as a disease. He worked out with a boxing coach, liked to have himself photographed in fighting gear, and cultivated the image that he was one tough m–f–, as he would have said. But in retrospect this all seems designed to hide the vulnerable soul that he really was.

This is evident not only in his soul searing playing of love songs, but the facts of his career. At three separate points in the early 1950s, early 1960s, and late 1970s, Davis was forced to take time off from his career to wrestle his inner demons. The first break was to cure himself of a heroin addiction he had picked up essentially in emulation of his idol, Charlie Parker. The last as he bragged in his autobiography, he devoted to the pursuit of what were then known as “recreational drugs” and kinky sex.

It is the middle sabbatical, however, that we’re interested in. For this was when two of the strongest elements of his personality – the need for artistic evolution and the need for mentalphysical healing – coalesced into a remarkable development in his music.

In 1960, Davis had released “Kind of Blue” and “Sketches of Spain” – two milestones of his early career. But in 1961 and 1962, he was forced to take a lot of time off, in part to deal with illness. His infrequent performance schedule forced bassist Paul Chambers and drummer Jimmy Cobb to leave his quintet. These were the last two remaining members of the great Davis group of the 1950s, which at times had included John Coltrane, Cannonball Adderley, Bill Evans, Red Garland, Wynton Kelly, and Philly Joe Jones. Chambers had been with the trumpeter since 1955, and was the only musician who stayed with Davis for the entire duration of his spectacular maturation.

With Chambers and Cobb gone, Davis began in earnest to look for new musicians and new directions. In the two years documented by the current box, Davis completed only three studio sessions. He hooked up early with the fine, Memphis-born tenor saxophonist George Coleman, whom Coltrane had recommended. Coleman stayed on for about a year.

Together they did two studio sessions in Los Angeles with the remarkable British composer and multi-instrumentalist Victor Feldman.

These dates, from April 1963, resulted in two all-time Davis classics, both written by Feldman. On “Joshua,” a memorable bop line grows faster in each of the four versions (live and studio) in this package. “Seven Steps to Heaven,” as the title implies, is essentially a line of seven ascending notes, and one of the catchiest things that Davis ever played. I only wish Feldman had collaborated more extensively with Davis.

Apart from this very new music, the two California dates resulted in expressive treatments of some very old music, two blues songs by the African-American composers Clarence Williams (“Baby, Won’t You Please Come Home”) and Spencer Williams (“Basin Street Blues”), as well as “Summer Nights,” a ballad by Hollywood songster Harry Warren. These tracks, all done by just the trumpeter and the rhythm section, are highly abstract, with melodies that old-time fans familiar with the tunes might not recognize. But they’re all achingly beautiful.

A month later, Davis did a session in New York, but shortly afterwards Columbia Records, without Davis’s knowledge, released “Summer Nights” as part of a poorly conceived compilation album called “Quiet Nights.” Davis was so disgusted that he boycotted Columbia for two years, refusing to go into the studio and to fill his contractual obligation to allow the label to record his live concerts.

Like many musicians, Miles Davis preferred to experiment with new material in the studio – to see how it sounded – and only play the stuff he knew that worked really well for crowds that were paying to see him. Thus, for most of the four concerts that constitute the bulk of this set (Antibes, Philharmonic Hall in New York, Tokyo, and Berlin), Davis concentrates on repertoire he had been playing since the Coltrane days. Because of his inclination to constantly take chances, however, these familiar selections sound very different from the classic recorded versions that we know.

Another reason they sound different is that the lineup wasn’t quite settled. By this time, he had four-fifths of his great 1960s quintet, including the whole rhythm section: Herbie Hancock on piano, Ron Carter on bass, and the 17-year-old percussion wunderkind Tony Williams. He was still searching for the perfect other half of his front-line, a tenor player to fill Coltrane’s shoes and serve as contrast for his tightly pinched and piercing trumpet. The Davis bands were always a mixture of hot and cool, introvert and extrovert, and in these concerts you can hear him looking for the right match.

All three tenor players represented here were decidedly post-Coltrane. Mr. Coleman, who is extensively featured on both the Antibes set and the New York date (which was a full two-hour concert), was the most traditional. Sam Rivers, who replaced Mr. Coleman on the Tokyo Concert, was and is the most far-out; he remains a major figure on the avant-garde scene, and it’s tempting to speculate about the music he and Davis would have made had they continued working together.

Wayne Shorter, who completed the quintet in time for the Berlin Concert, was in retrospect the perfect choice. They had worked together in a one-off session in 1962 and Davis had tried to hire him then. Mr. Shorter demurred at the time, saying he didn’t want to leave Art Blakey’s Jazz Messengers just yet. But when he did join up with Davis, he remained the trumpeter’s key collaborator.

The most fascinating thing about this set is hearing Davis in contrast with these three great players and charting the evolution of one of the most refreshing group sounds in jazz – a sound as startlingly imaginative as those of John Coltrane’s and Ornette Coleman’s classic quartets. As usual with Davis’s groups, there’s very little traditional interplay between the two lead horns, as well as very little ensemble playing. On the surface, it sounds mostly like a lot of very long solos. But listen closer and you can hear the five men constantly listening to one another and playing off on another, and Davis himself sounds different with each.

By the time these recordings were made, Davis was one of jazz’s only bona fide superstars, the envy of both fans and fellow musicians for his celebrity, fast cars, and women. Yet you couldn’t give me twice what Davis got to have to endure his constant pain or his restless soul-searching. His was a soul that seems to have never known peace. No matter what the rewards were, when you measure them against everything he gave us, it still seems he was under compensated.