If you haven't heard it, take a few seconds to hear President Barack Obama sing a bar of the Rev. Al Green's "Let's Stay Together." The crowd went nuts, and now the youtube video has gone viral.

http://www.youtube.com/watch?v=T-hDt2E8MoE

Obama was on stage at the Apollo Theater in New York and was thanking people for attending an event when he sang.

Other musical presidents

Obama is not the first president to show his tuneful side to the public. Through the years, commanders-in-chief have turned musicians-in-chief, with varying results.

Among them:

RICHARD NIXON. He was no Billy Joel. And yet twice in 1974, in the last months of his doomed administration, the President Who Was Not a Crook became the President Who Was the Piano Man. He played "God Bless America" at the Grand Ole Opry, and the same tune when he accompanied singer Pearl Bailey in the East Room of the White House. The two also conspired on "Home on the Range" and "Wild Irish Rose." ''You don't play as well as I sing," Bailey joked, "but I don't sing as well as you govern." She was half right.
Nixon also appeared on TV with Jack Paar in 1963, and played a little concerto of his own devising. Nixon said this would put the kibosh on his political career: "The Republicans don't want to another piano player in the White House," he said.

HARRY TRUMAN. Nixon was referring to "Give 'em Hell Harry," a Democrat who could never pass a piano without sitting down to play a few bars. In 1952, Truman conducted a nationally televised tour of the newly renovated White House and played a bit on the 1938 Steinway. The building had been condemned when a leg of piano played by his daughter Margaret, a singer whose talent was of some dispute, crashed through the floor of the decrepit mansion.

Truman also played for Joseph Stalin and Winston Churchill at the Potsdam Conference, neither shortening nor lengthening World War II appreciably. The man did love the piano: "My choice early in life was either to be a piano-player in a whorehouse or a politician," he once said. "And to tell the truth, there's hardly any difference."

THOMAS JEFFERSON. He played the violin, and not just to meet women (though that is how he came to know his harpsichord-playing wife, Martha). When he wasn't writing the Declaration of Independence or rewriting the Bible or inventing a four-sided music stand for string quartets, he made music. He played the cello and clavichord, but the violin was his instrument, and he was a ringer for several orchestras. Though often in need of money, he always refused payment.

BILL CLINTON. William Jefferson Clinton, not yet president, took a giant step in that direction in June 1992 when he showed up with a saxophone and wraparound sunglasses to play "Heartbreak Hotel" on "The Arsenio Hall Show." ''It's nice to see a Democrat blow something besides the election," quipped the host.

After he won the presidency, Clinton played with E Street Band saxophonist Clarence Clemons at an inaugural ball. He also took a moment from an East European tour in 1994 to climb the stage of Prague's Reduta Jazz Club and play "My Funny Valentine" and "Summertime." At one point he invited Czech leader Vaclav Havel to join him; this would be remembered in political and musical history as the Two Presidents Gig.

Many other chief executives performed, though not necessarily in public. John Quincy Adams played the flute, Chester Arthur the banjo, Woodrow Wilson the violin. Franklin Roosevelt liked to sing. And John Tyler — of "Tippecanoe and Tyler, too" fame — organized his 15 children in a White House minstrel band. Historian Elise Kirk says this probably included banjo, bones, drums and guitar. Plus a country fiddle.

Mercifully, no videos exist.
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AP contributed to this report. News Researcher Rhonda Shafner contributed to the AP report.