Just in case anyone still wants to know why B.B. King sings the blues, the 78-year-old legend complained at Wolf Trap Sunday night that Viagra is of little use to a diabetic. Fortunately, King still has Lucille, his famous Gibson guitar, to keep him company, along with three generations of fans.

Bad knees have forced King to remain seated throughout his concerts these days. But he still shakes from head to toe when the rhythm moves him, still rears his head back when Lucille sighs and cries, still shouts out a lyric with the blunt force of a pulpit-pounding preacher. Sunday night he was in a particularly jovial and expansive mood, frequently chatting with the crowd and enlisting its vocal support. But he and his horn-powered band also tended to business while reviving "When Love Comes to Town," "The Thrill Is Gone" and other favorites. A hornless interlude found him moving beyond blues, slowly drifting into the country lope of "You Are My Sunshine" and showcasing Lucille's stirring voice during a terrific reprise of "Summertime." If he hadn't spent so much time repeatedly introducing his band mates, King could have played an additional tune or two. But Lucille, eloquent as ever, didn't waste a note.

The opening set by Dr. John was a Crescent City party-starter, sparked by old hits and vibrantly syncopated quartet arrangements of several tunes off his new CD, "N'Awlinz: Dis, Dat or D'udda."

-- Mike Joyce

King, shown in 2003, entertained the crowd with his beloved guitar Lucille.