Taj Mahal was teaching the Museum of Natural History crowd last night how to clap and sing on the old blues, "Hold That Wood Pile Down." He wouldn't tolerate any sloppy hand-clapping and insisted: Find that beat. Afterwards, he admitted, "These old-time styles you don't hear every day, so it takes some getting used to. By the end, though, you sounded really good." The concert kicked off the Smithsonian's weekend conference on "Black American Blues Song." Emcee Bernice Reagon (of Sweet Honey in the Rock) said the conference was supposed to educate as well as entertain. The evening's performers -- Taj Mahal, Willie Dixon, Koko Taylor and J.C. Buris -- proved that with the blues there's no difference between learning and enjoying.

The concert's centerpiece was Dixon, who ranks with Robert Johnson as one of the two greatest blues songwriters of all time. Leading a powerful Chicago sextet that included his two sons and the legendary Sugar Blue on harmonica, he proved that he's a charismatic performer, too. He introduced every song with a philosophical monologue on the nature of the blues. Instead of his well-known classics, Dixon emphasized newer songs that were as witty and wise as any he or anyone else has written. "But You Can't Make Peace" was a bellowing antiwar song; "No Pie in the Sky" questioned religious superstitions and "Good Advice" was just that. "Today," Dixon explained, "we had to present this program for Washington and the president so they'd have a better understanding of the blues."

J.C. Buris began the show with the rural southern style that began the blues. Buris' field shouts and hand-muted harmonica style reflected the influence of his uncle, Sonny Terry. He supplied his own percussion with bones and gave a delightful lesson on hambone technique. Taj Mahal took old songs like "Sweet Home Chicago" and "Stagole" and changed them to his own designs. He stripped Dixon's "Spoonful" down to a bare outline -- scatting half the lyrics and letting his human-sounding electric guitar sing the title. He taught the crowd do-wop harmonies for his own "I'm Gonna Move Up to the Country" and regaled them on banjo and piano. He encored with "Johnny Too Bad" to prove that even Jamaica's reggae is part of the blues.

Koko Taylor closed the show with the evening's best vocal. Having rewritten Muddy Water's "I'm a Man" as "I'm a Woman," she screamed the first syllable of "woman" into a barely audible groan and then erupted into an octave-leaping roar of pride. Backed by her four-man Mean Machine, she moved effortlessly from whispered intimacies to belted demands. Mahal, Dixon, Taylor and Buris will repeat their concert tonight. They will join scholars for panel discussions on the blues during the day. Buris will join Washington's fine blues duo, Bowling Green John C. Cephas & Phil Wiggins for "Blues at Noon" tomorrow.