Bathed in a soft purple light, 59-year-old Robert Fripp took the stage at 9:30 club Monday without a word. Too bad the fans of headlining act Porcupine Tree weren't so tight-lipped. They often drowned out the most delicate passages of Fripp's nuanced set with a discourteous chatter that distracted fellow audience members, but never Fripp.

As the linchpin member of prog-rock legends King Crimson, Fripp earned his guitar-hero stripes in the '70s with a virtuoso style. But since the mid-'90s, Fripp has leaned toward what he calls "soundscape" work, an improvised and carefully paced series of melodic (or sometimes discordant) drones. Sure, Fripp's sonic ice shelf often unfolds at a, well, glacial pace -- but it can be beautiful stuff, especially if your attention span lasts longer than a Neil Peart drum fill.

Had inconsiderate audience members done their homework, they certainly wouldn't have treated the prog legend with such disrespect. Eerie hushes about 30 minutes into Fripp's performance exposed a restless chatter that had been building since he stepped onstage.

By the 45-minute mark, impolite prattle gave way to all-out heckling, with one boorish fellow hollering out "Play something else!" Seemingly unfazed, Fripp floated through the final dreamy passages of his set unperturbed. When the last drone faded, he didn't storm offstage -- he took a bow for those who paid to enjoy his work.

-- Chris Richards