Spectrum were formed in April 1969 in Melbourne, as a progressive rock group, by Mark Kennedy on drums (ex-Gallery), Lee Neale on organ (ex-Nineteen87), Bill Putt on bass guitar (ex-Gallery, The Lost Souls), and Mike Rudd on guitar, harmonica and lead vocals (ex-Chants R&B, The Party Machine, Sons of the Vegetal Mother). Initially the group drew on the work of contemporary bands such as Traffic, Soft Machine and Pink Floyd; they played cover versions of their material. Spectrum developed their own style as Rudd began writing original material. Alongside Kennedy's drum solos, Putt's bass playing and Neale's keyboard work, a feature of Spectrum's sound was Rudd's guitar playing — he eschewed the near-universal use of guitar picks – using a finger-picking style on a vintage Fender Stratocaster to develop a characteristic sound.