From Wikipedia:
"The Midnight Special is an American musical variety series that aired during the 1970s and early 1980s, created and produced by Burt Sugarman and airing on NBC. It premiered as a special on August 19, 1972, then began its run as a regular series on February 2, 1973; its last episode was on May 1, 1981.[2] The ninety-minute program followed the Friday night edition of The Tonight Show Starring Johnny Carson.
The show mostly featured guest hosts, except for a period from July 1975 through March 1976 when Helen Reddy was the regular host. Wolfman Jack served as the announcer. The theme song, a traditional folk song called "Midnight Special", was performed by Johnny Rivers.
The Midnight Special was noted for featuring musical acts performing live, which was unique since most television appearances during the era showed performers lip-synching to prerecorded music. The series also occasionally aired vintage footage of older acts (such as Bill Haley & His Comets)."