From wiki:
Rocky Top
Rocky Top
Vol fans can also thank Julian, via Walter McDaniel, for introducing "Rocky Top" in a halftime show in 1972, after which it made its way to the stands. The football crowd loved the tune and its words; the more the band played it, the more people wanted it. It has now become one of the University's best-known traditions and one of the band's most famous songs.
Its popularity also extends far beyond the campus of the University of Tennessee; "Rocky Top" became one of the Tennessee state songs in 1982. To acknowledge the impact that UT and the "Pride" had on their careers, when writers Felice and Boudleaux Bryant were inducted into the Songwriters Hall of Fame in 1986, Julian was invited.
Contrary to popular belief, "Rocky Top" is not Tennessee's official fight song, although it is so closely identified with the university that many believe this to be the case. Tennessee's official fight song is "Down the Field". It is quite common for the band to end playing Rocky Top and the crowd to continue singing the chorus into the next play.