Prog is an adventure: a bridge between pop immediacy and classical structure that challenges musicians and fans alike. At the turn of the ‘70s, the sudden shift in musical emphasis from singles to albums gave rock bands a chance to stretch out and investigate grooves not built for dancing and plangent melodies that take the ear on an emotional gallivant to unexplored locations. Inspired by symphonic form, the rigours of modern jazz, and great works of literature, prog rockers such as King Crimson, Yes, and Emerson, Lake & Palmer set out to discover different sonic landscapes and create a new language for popular music. This questing spirit—upheld in subsequent years by The Mars Volta and Muse—encourages longer song suites as musicians wrestle with uncanny time signatures, dense mystical poetry, and devilish chord structures on an eternal quest to find the lost chord.