The Greenwood brothers attended the independent boys' school Abingdon, where they formed a band, On a Friday, with singer Thom Yorke, guitarist Ed O'Brien, and drummer Phil Selway. Jonny had previously been in a band called Illiterate Hands with Matt Hawksworth, Simon Newton, Ben Kendrick, Nigel Powell and Yorke's brother Andy Yorke. The youngest member of On a Friday, Greenwood was two school years below Yorke and Colin and the last to join. He first played harmonica and then keyboards, but soon became lead guitarist. Greenwood studied music at A Level, when he studied chorale harmonisation.