Obama lent his voice to a White House jam featuring Mick Jagger, B.B. King, Jeff Beck and Buddy Guy on Tuesday during a celebration of blues and its influence on modern pop culture.

After wowing crowds in January by singing a line from Al Green's classic hit "Let's Stay Together" at a Harlem fundraiser, the President sang a verse of "Sweet Home Chicago" in the all-star finale of a TV special taped at the White House.

"We were trying to get you to help us sing. I heard you singing Al Green," blues guitar legend Guy hollered to Obama on Tuesday. "So you started something. You got to keep it up now. You can do it."

Taking a microphone handed to him by Rolling Stones frontman Jagger, a smiling Obama sang a solo verse of "Sweet Home Chicago" before handing back to the band.

The performance was part of a PBS television special marking

Black History month that will be broadcast on February 27 as "In Performance at the White House: Red, White and Blues," the public broadcaster said.

Obama's blues solo recalled Clinton's saxophone playing appearance in 1992 on the "The Arsenio Hall Show", which was credited with boosting his presidential campaign.

Obama's brief rendition of "Let's Stay Together" in January helped increase sales of the 1971 Al Green classic by 490 percent in the following week, according to Billboard magazine, and the YouTube video has been viewed more than 7 million times.

(Reporting By Jill Serjeant; Editing by Bob Tourtellotte)

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