New Order’s 'Blue Monday' is the best-selling 12-inch single of all time. It bridged the gap between 70s disco and 80s dance music. The song is famous for its mechanical, driving beat, but one of its most unique features—the choir-like synth sound—was an accident. The band had just bought an early sampler (an Emulator) and was experimenting with it when they discovered they could sample their own voices and play them back as a keyboard instrument. The single’s original die-cut sleeve, designed by Peter Saville to look like a floppy disk, was so expensive to produce that the band’s label, Factory Records, reportedly lost money on every copy sold. Despite this, it became a massive club hit and reached the top 10 in the UK. It remains a cornerstone of electronic music and a definitive 'alternative' hit.