Bob Harris continues his journey through the world of Album Orientated Rock [AOR]. Powered by the West Coast experimental music scene and the release of the Beatles' Sgt. Pepper LP, AOR first burst onto American radio in San Francisco in 1967. It was a revelation, a tour de force of creative programming which empowered its DJs and provided an antidote to the Top 40 hit radio that just wasn't "hip" anymore. By the mid-70s, AOR had become the most successful radio format in America. The A-Z of AOR plays the biggest hits and the hidden gems from a genre that drove album sales into the triple millions. Boston, Rick Springfield, Pat Benatar and Supertramp are amongst the artists featured this week.