By Keith Caulfield, Los Angeles

Al Green's "Let's Stay Together" got a sales boost last week from an unlikely source -- President Barack Obama.

A video of the president singing the first line of the song at a Jan. 19 fund-raising event went viral the next day, sparking a 490% weekly sales increase for the song. It sold 16,000 downloads in the week ending Jan. 22 according to Nielsen SoundScan.

It's the best sales week for the song since SoundScan began tracking downloads in 2003.

The fundraiser took place at New York's Apollo Theater, where Green was also making an appearance. As Obama took to the stage, he noted Green's presence in the room and surprised the crowd (and his aides) with a bit of his crooning.



"Those guys didn't think I would do it," joked Obama, gesturing to his staffers on the side of the stage. "I told you I was going to do it. The Sandman did not come out."

While there are multiple videos of the moment on YouTube, the most-viewed clip has been watched more than 4 million times.