He may be their No. 1 fan

Brad Mehldau did it first with his jazz piano, working Radiohead’s “Exit Music (for a Film)” and “Paranoid Android” into his albums as early as 1998. But Los Angeles-based classical pianist Christopher O’Riley has taken an obsession with the English rock band to its logical conclusion: playing all Radiohead, all the time.

At two sold-out shows on Friday at the Knitting Factory Hollywood, an affable O’Riley chatted with the crowd and trounced his ambitious, kinetic arrangements, white button-down shirt pulled casually out of his jeans.

But the performance was fascinating mostly for the purity of the obsession with Radiohead he seemed to share with most everyone in the room.

Kicking off with “Airbag,” from the band’s 1997 breakthrough statement, “OK Computer,” O’Riley attacked 18 arrangements that were both reworkings and mimetic exercises. His versions were often differently paced and denser than the originals, and yet he seemed bent on finding clever sonic approximations of vocal parts, electronic marginalia and off-melody signatures whose absence would be missed by true fans.

On “Motion Picture Soundtrack,” for example, he filled the background behind the simple melody with blazing runs up and down the keyboard to mimic a harp part in the original. Though he clearly enjoyed the soaring, sweet parts of each song, O’Riley never reduced the compositions, always maintaining their complex character.

Despite his obvious talent, however, O’Riley knew he was playing only to hard-core fans, even asking for a vote on songs to play in the middle of the set, and settling on a B-side called “Polyethylene Part 2.”

Describing himself as the “biggest geek in the room,” he asked whether he should play “Good Morning Mr. Magpie,” which Radiohead singer Thom Yorke played solo only once, on a Christmas Webcast. By the time he got to his second encore, “True Love Waits” (also the title of his album of Radiohead hits), even the crowd’s standing ovation couldn’t diminish the feeling that these were only brilliantly played substitutes for the real songs.