It has two front chainrings and ten cogs in the rear. A 3x9 has three front chainrings and nine cogs in the rear. Although bikes used to have all types of drivetrains with 5, 6, 7, or other numbers of rear cogs, were going to start our discussion with 9-speed systems.
Neil Sedaka has a long and distinguished career as a pop singer, songwriter, and pianist. His many hits include Breaking Up Is Hard To Do (1962, 1975 slower remake), Laughter In The Rain (1975), and Bad Blood (1975).
Something the Led Zeppelin song never did. Sedaka's Stairway To Heaven was recorded with Stan Applebaum and his Orchestra, on the RCA Victor label. It was his sixth single, and in the UK was released in March 1960 backed by Forty Winks Away.