The 1970s were a rich time for music. The charts were dominated by Abba, with their distinctive dress sense and catchy pop hits. Blondie brought some New York punk energy to a clutch of lively numbers and Dylan gave us his anthemic Knockin' On Heaven's Door .The 1970s also saw the release of John Lennon's eternally relevant piece Imagine , and the arrival of new kid Elvis Costello with his hit Oli…