When is the blues not the blues? The answer is: a lot of the time. The blues is, in fact, an inherently deceptive music. When David Rose writes a song called “Our Waltz,” it has no choice but to be in 3/4 time; when Frankie Yankovic plays the “Too-Fat Polka,” you know it’s got to be a genuine polka. A mambo is a mambo and a march is always a march.

But Harold Arlen can write “Blues in the Night,” and it isn’t an authentic 12-bar blues at all. Duke Ellington’s simply (but deceptively) titled “The Blues” isn’t even remotely in blues form. In 1938, the ultra-traditionalist Mezz Mezzrow wrote a tune (and, later, a memoir) called “Really the Blues,” in hopes of ending all confusion — but Johnny Mandel and Woody Herman countered 11 years later with “Not Really the Blues.”

So when a jazz icon such as Miles Davis titles an album “Kind of Blue,” admitting right off the bat that the music contained within isn’t completely blue, you know something’s up. Released in 1959, this seminal album is generally acknowledged as the single greatest jazz recording of all time; if you only own one jazz album, chances are it’s “Kind of Blue.” That’s probably why Columbia Records (now Legacy Recordings) continually shows its appreciation by constantly reissuing the album in ever-expanding packages. This month, the label will release “Kind of Blue: 50th Anniversary Collector’s Edition” (because 49 is, er, just as good as 50) in the most deluxe boxed set of all, containing two compact discs, a DVD, an audiophile replica of the original LP, and a 60-page hardcover book. That’s a lot of blue.

Personally speaking, “Kind of Blue” has never been my favorite Miles Davis record; I listen to “Miles Ahead” and the other two heavyweight collaborations with Gil Evans. Yet “Kind of Blue” has a cachet like no other album — jazz, pop, or classical — in the history of music. It may be the best-selling jazz album in history, but it wasn’t even the most successful jazz release of 1959. That honor belongs to a different Columbia LP, Dave Brubeck’s comparably innovative “Time Out” — another album I listen to more frequently than “Kind of Blue.”

Like “Kind of Blue,” “Time Out” telegraphs its intentions in the title, because it experiments with its titular element. Yet you will never find a Dave Brubeck album on the list that Rolling Stone magazine calls, with an unmatched combination of vagueness and egotism, “The 500 Greatest Albums of All Time.” Of course, the magazine means rock ‘n’ roll (or, to be more specific, post-1955 pop), which would be fine if it just came out and said that. If it truly meant to cover all music, the Bach B-Minor Mass or “Don Giovanni” would be no. 1. But to include a token handful of landmark jazz albums — and put Frank Sinatra’s “In The Wee Small Hours” at no. 100 — is just insulting.

However, in the case of “Kind of Blue,” seeing that Rolling Stone has listed it at no. 12 — by far the highest-positioned non-rock release in the list — is actually informative, and shows the degree to which appreciators of rock and pop have embraced the album through the years. In the booklet to the new boxed set, Francis Davis catalogs an impressive pedigree of pop performances in the last four decades that have borrowed from “So What” (the opening, and catchiest, tune on “Kind of Blue”), including James Brown’s “Cold Sweat” and “recent hits from Amy Winehouse and Christina Aguilera.”

I can’t imagine any of them listening to Dave Brubeck. But it’s the very fact that “Kind of Blue” plays with the fundamental elements of the blues, which are the basis of much of rock ‘n’ roll, that makes the difference. Certainly, it is more central to the pop experience than Mr. Brubeck’s experiments with Turkish time signatures (even though “Take Five” was actually a hit single in 1959).

“Kind of Blue” is justly celebrated for the way it looks backward as well as forward: It was the first all-out use of modal improvisation in jazz, arriving on the table at virtually the same time as Ornette Coleman’s new “free” jazz, which also showcased a new approach to harmony and form. As it turned out, rock-based improvisation would eventually go the same way, from blues-benders such as Carlos Santana and the Allman Brothers to postmodern classicists such as Steve Reich and Philip Glass. Yet modal music is an ancient concept, considerably older than the Western rules of major and minor scales. By combining ideas that were born before Bach with elements of the blues, another very old form, Miles Davis and company were certainly on to something new as the 1960s dawned — and something old at the same time.

As on the trumpeter’s “Birth of the Cool” album from 10 years earlier, the ensemble on “Kind of Blue” is at once an all-star group and a regular working band, an amazing confluence of iconic musicians that actually played together in front of real audiences. If “Kind of Blue” is the “Sgt. Pepper’s Lonely Hearts Club Band” of jazz, its Fab Four principals (with no disrespect to the enormously important bassist Paul Chambers and drummer Jimmy Cobb, and guest pianist Wynton Kelly, who plays on “Freddie Freeloader”) were a disparate group of musical personalities who didn’t seem capable of occupying the same stylistic universe, let alone the same bandstand.

The leader was Davis, a sensitive soul who lived much of his life in acute physical pain yet managed to convince the world he was the ultimate swinger. He was the original blaxploitation star, a combination of Richard Roundtree and Isaac Hayes — only two decades before the fact. Pianist and chief co-composer Bill Evans was a college professor type who achieved a zen-like unity with his instrument. Filling out the group were two diverse spiritualists of the saxophone: the outwardly directed Cannonball Adderley, who played like a rabble-rousing Deep South “country preacher,” and the more inner-directed John Coltrane, representing the kind of holy man who sits, unmoving, on a mountaintop for days, contemplating the essence of God.

Roughly a third of what’s included on the new boxed set is the original album. Columbia has also given us one complete alternate take (“Flamenco Sketches”) and some fascinating studio chitchat, plus the only other studio session by this edition of the sextet (from May 1958), with Evans and Adderley joining the long-standing Davis-Coltrane combination. There’s also a very different live performance of “So What” from 1960.

Even though only “Freddie Freeloader” and “All Blues” utilize true 12-bar blues form, the blues runs throughout these five songs and 45 minutes of sound that changed the world. It’s an appropriately monumental package for a milestone work that’s more than kind of classic.

wfriedwald@nysun.com