If there were an encyclopedia of late 20th century popular music — a definitive compendium of artists, albums, genres, movements, slang, scenes, debuts, ODs, legends and all the other little details that make music worth loving — the listing for “bootleg” would read something like: “A recording illicitly produced, bought or sold. See also: Dylan, Bob.”

No other artist, not The Beatles or the Stones or Michael Jackson or the Grateful Dead, has attracted fans and followers of unofficial recordings in comparable quantity or fervor as Bob Dylan. No other artist has presented the same Delphian combination of mystery, wisdom, directness and inspiration that defines Dylan’s musical persona; to fully understand him as an artist is as impossible a task as assembling a complete collection of Dylan’s full ­— that is to say unofficial — catalog.

Ever since Robert Zimmerman became Bob Dylan, fans have collected and traded unofficial recordings by the enigmatic (and prolific) artist. Tapes include everything from home recordings to live shows to interviews to demos to outtakes to alternate versions. For decades, bootleg recordings were the domain of Dylan’s most rabid fans, an elite group — some of whom view collecting the artist’s unofficial recordings as a spiritual more than musical pastime. That’s how things were until ’91, when Dylan’s longtime label, Columbia, released The Bootleg Series: Vols. 1-3 (Rare & Unreleased), a three-disc collection of non-album tracks that spanned Dylan’s career from Greenwich Village coffeehouses, civil rights rallies, electric inspiration, motorcycle accidents through to the supposed “third comeback” and the inception of the Never-Ending Tour in the late ’80s.

Since then, some of the most historic performances of Dylan’s career have been released; live recordings from ’75’s Rolling Thunder Revue tour, ’64’s Carnegie Hall performance that marked the apex of Dylan’s acoustic career and the essential ’66 Free Trade Hall show during which a wild-haired Dylan, backed electrically by touring band The Hawks, was denounced by a dissatisfied folkie as “Judas!”

The most recent installment in the series, The Bootleg Series, Vol. 7: No Direction Home — The Soundtrack, doesn’t capture the music made on one evening or one tour; this release is meant to accompany the story of Dylan’s ascension as a controversial folk poet and his controversial “second coming” as the new musical landscape’s electric messiah, which is shown in the upcoming Martin Scorsese-directed documentary of the same name, airing Sept. 26 and 27 on PBS. No Direction Home’s first disc is comprised mostly of early and live recordings from Dylan’s acoustic years, including what most believe to be the first recording of his music in existence (opener “When I Got Troubles,” whose faded, crackly quality and bluesy simplicity is reminiscent of selections from the Anthology of American Folk Music, which may have had a hand in inspiring it). Dylan’s fascination with folk legend Woody Guthrie shows on recordings of “This Land Is Your Land” and one of only two self-penned songs on his first album, “Song to Woody.” These tracks exhibit Dylan’s fascinating experimentation with persona early in his career; on “Troubles” and the home recording of “Rambler, Gambler,” Dylan’s voice is youthful, almost sweet; he sounds like a barefoot Appalachian boy whose only contact with the outside world comes from fuzzy transmissions of blues and country radio shows from the Tennessee Valley. By the time he recorded “Song to Woody” and “Dink’s Song,” Dylan’s voice had aged and hardened to that familiar nasal rasp of gravel and soul that characterizes the folk classics (“Man of Constant Sorrow”), social commentary (“Blowin’ in the Wind,” “Masters of War”) and pre-psychedelic epic visions (“Mr. Tambourine Man”) that made the singer/songwriter from Minnesota into a cultural vanguard.