You've probably never bought a CD by The Roots.

The Philadelphia-based hip-hop collective's two biggest-selling recordings — 1999's "Things Fall Apart" and 2002's "Phrenology" — have moved only slightly more than a half-million copies each. Sales of the five remaining albums may collectively total less than a million.

The Roots' biggest hit on Billboard's rap singles chart? "What They Do," which peaked at No. 5. (Pause.) In 1997.

So if you're not a dyed-in-the-'fro Roots Head with tickets in hand, why bother checking out founding trifecta drummer Ahmir "?uestlove" Thompson, emcee Tariq "Black Thought" Trotter, bassist Leon "Hub" Hubbard and the rest of the band at the Pipeline Cafe on Thursday?

Easy. The Roots wouldn't know how to be musically unoriginal if they tried.

?uestlove and Black Thought founded The Roots 16 years ago while still in high school. Instead of DJ tools neither could afford — turntables, a mike, a mixer, crates of vinyl — they used ?uestlove's basic drum kit and, eventually, real players of instruments.

A sample-free, instrument-rich and genre-defying musical environment became The Roots' calling card; a conscious, intelligent lyrical flow the Krazy Glue that holds all of it together.

Need another reason to go? The Roots, with their improvisation-heavy onslaught of percussion, bass, keyboards and rhythm and lead guitar, are said to be at their best live.

Unfamiliar with the band or just craving the opportunity to compare notes on your collection of Roots CDs? I revisited my own Roots CD collection recently and ranked the band's most notable discs on a must-own scale of 1 (skip it like The Pussycat Dolls debut) to 5 (buy it now, or risk my sending you The Pussycat Dolls debut).

Enjoy the following discs again or for the first time. Just one more word to the uninitiated: Pray the boys from Philly bust "The Seed 2.0" live at the Pipe.

The Roots' second album, following the low-key 1993 indie debut "Organix," is often a bit heavy on the lengthy improvisational jams. The band would learn to temper and refine that in later recordings. But The Roots here are already adept at keeping their old-school chunky grooves laid-back loose and wonderfully sample free. The warm, playing-live-in-the-next room sound brings a cool dreaminess to tracks like "Lazy Afternoon," "Mellow My Man" and "Datskat."

Must-own rating: 3

"ILLADELPH HALFLIFE" (1996, NO. 21)

The band's third disc finds The Roots embracing its still-new, well-earned street cred by churning out grooves and lyrics more spare than ever before. The jamming still too often seems endless. But wrapped in dense percussion-heavy funk fests ("Clones") and elegantly mesmerizing quiet-storm keyboards ("What They Do"), The Roots' commentary on the positives and negatives of inner-city American life is skillful and remarkably eloquent. On the guest list: Raphael Saadiq, Common, Cassandra Wilson, Q-Tip and D'Angelo.

Must-own rating: 3

"THINGS FALL APART" (1999, NO. 4)

Scary good and crazy revolutionary. On this fourth disc, The Roots come out as a hip-hop — not alternative hip-hop — force to contend with. The streets are still the subject, while musical experimentation and improvisation rooted in jazz theory and neo-soul takes hip-hop into new kinetic realms. "You Got Me," on which Erykah Badu lends reflective, emotion-rich vocals over evocative flow from Black Thought and a restless drum-n-bass-reminiscent exit courtesy of ?uestlove, should be on every love-themed mix CD. The Roots' first great album.

Must-own rating: 5

"THE ROOTS COME ALIVE" (1999, NO. 50)

Many fans coming away from a Roots live show swear that as good as the band's studio work gets, nothing really compares to its onstage skills. I'll save my own opinion for the Pipeline Cafe gig. In this set recorded at tour stops in New York and Paris, The Roots come off a bit too cool for their own good at times. Still, the band's sweetest skills — ?uestlove's minimalist jazz-funk drumming and Black Thought's bobbing-and-weaving flow — make this live document worth the cost: a bargain $6.99 on iTunes.

Must-own rating: 3

"PHRENOLOGY" (2002, NO. 28)

This one —The Roots' fifth and best studio work — is musically and lyrically confident, clever and brilliant from beginning to end. The Roots become hip-hop innovators on a legendary scale. Just try picking out favorites. Wall-of-sound production and killer Cody ChesnuTT vocals flavor the anthemic "The Seed (2.0)." Mind-blowing riot gear percussion throttles the bombastic flow of "Thought @ Work." Black Thought delivers a fierce slap upside the head of gangsta rap in "Rock You." Magnificent neo-soul grooves move "Complexity" (with Jill Scott); a coda of mind-warping sonics flood "Water." Amazing stuff.

Must-own rating: 5

"HOME GROWN! THE BEGINNER'S GUIDE TO UNDERSTANDING THE ROOTS, VOL. 1 & 2" (2005, NOS. 161/187)

Beginners would be better off avoiding this ill-named, oddball collection of ?uestlove-selected favorites, rarities, remixes and live tracks. Come on, ?uest! A rambling, self-indulgent medley that merely includes a snippet of "The Seed" instead of "Phrenology's" addictive original? "You Got Me" with no "I'm a tell you" Badu? A sound-check version of "Break You Off"? For beginners? Please. If you're really starting your Roots archive, pick up "Phrenology" and "Things Fall Apart" first.

Must-own rating: 4 (for fans with everything else); 2 (for the rest of the world)

"THE TIPPING POINT" (2004, NO. 4)

The Roots took some critical drubbing here for returning to earth a bit empty on surprises after the freewheeling cosmic musical trip that was "Phrenology." (OutKast's genre-redefining "Speakerboxxx/The Love Below" still ruled in 2004.) But The Roots' seventh album is a solid collection of what the band does best — leading rather than following hip-hop's ruling wack pack, and (especially on "Don't Say Nuthin'") teasing folks holding out hope they'll one day turn G-Unit club-ready.

Must-own rating: 4

Reach Derek Paiva at dpaiva@honoluluadvertiser.com.