Synth-pop barely begins to describe Pet Shop Boys' stylistic breadth. On 1987's “Nothing Has Been Proved,” they evoked ‘60s pop alongside iconic singer Dusty Springfield. Teaming up with Peter Rauhofer as The Collaboration, they kicked out a storming cover of the house classic “Break 4 Love.” Their remix of David Bowie's “Hallo Spaceboy” similarly pushes deep into peak-time club territory.