"Was this the children’s revolution, and was it being televised?" writes Ethan Gilsdorf. (Courtesy WGBH) Half a century later, I can still sing the address: "Write Zoom. Z, double-O, M. Box 3-5-0.

For pre-teens watching TV in the early 1970s, the opening to Zoom was captivating with seven, charismatic, barefoot kids in rugby shirts running, jumping, dancing and singing on a bare stage. They ...