on september 6, 2007, dave matthews band performed a free concert for the virginia tech student body and faculty. the show was entitled "a concert for virginia tech" and was done in memory of the shootings that took place on april 16, 2007. john mayer, phil vassar, and nas joined them. there were over 50,000 people in attendance. two days later, they performed a benefit show at atlanta's piedmont park with the allman brothers band opening. though only 75,000 tickets were sold (50,000 originally, then a second block of 15,000) nearly 20,000 people sneaked into the show, making it the largest one-day concert in atlanta history. the show raised money for the piedmont park conservancy association. it was released as a cd/dvd called live at piedmont park.