From Wikipedia:
Initially airing as a one-shot episode of the NBC television show Startime (season 1, episode 32) on 24 May 1960, Sing Along with Mitch went on to become a weekly series in 1961 as a community sing-along program hosted by Mitch Miller and featuring a male chorus: which was, basically, an extension of his series of Columbia record albums of the same name. In keeping with the show's title, viewers were presented with lyrics at the bottom of the television screen, and while many insist there was a bouncing ball to keep time, Miller correctly said this was something they remember from movie theater Screen Songs and Song Cartunes sing-along cartoons.
Singer Leslie Uggams, pianist Dick Hyman, and the singing Quinto Sisters were regularly featured on Sing Along with Mitch. One of the singers in Miller's chorale, Bob McGrath, later went on to a long and successful career on the PBS children's show Sesame Street (he was a founding member of the "human" cast in 1969 and McGrath became its longest-serving cast member until his enforced retirement in 2016). One of the show's trademarks was the final number, a group sing-along with the regular house chorale, among whom would be an uncredited celebrity not necessarily known for their singing ability, who was dressed like the others. "Hidden" guests in this closing singalong included Johnny Carson, Jerry Lewis, George Burns, Shirley Temple and Milton Berle.
As the popularity of the TV show rose, Miller produced and recorded several "Sing Along with Mitch" record albums, complete with tear-out lyric sheets.
Sing Along with Mitch ran on television from 1961 until the network canceled it in 1964, a victim of changing musical tastes. Selected repeats aired briefly on NBC during the spring of 1966. The show's primary audience was over the age of 40 and it did not gain the favor of advertisers targeting the youth market.