Singer-songwriter Paul Simon, a New York native, played an emotional rendition of his classic song, ‘The Sound of Silence,’ at the Twin Towers Memorial Service this morning (Sept. 11, 2011) to mark the 10th anniversary of the 9/11 tragedy.

“Hello darkness, my old friend. I've come to talk with you again,” he crooned, strumming his acoustic guitar as the crowd -- including victims' relatives and dignitaries -- assembled on the Twin Towers site.

Today, of course, is a day to look back on the horrific terrorist attacks on the World Trade Center and the Pentagon that brought down the Twin Towers a decade ago, claiming the lives of 3,000 innocent citizens.

Later today, President Obama is excepted to make an appearance for a special ceremony.

This wasn't Paul Simon's only New York City appearance this year. Earlier this summer, Simon invited former Talking Heads vocalist David Byrne to make a surprise guest appearance at his small theater performance at New York’s Webster Hall.

Watch Paul Simon Play 'The Sound of Silence' at Ground Zero:

More From Ultimate Classic Rock