Prog rock was all the rage in England circa 1970. Groups such as Yes and Genesis released long, complex works and suddenly saw masses of young men flocking to their concerts. Pink Floyd were the perfect band for this time. Atom Heart Mother, their fifth album in a mere three years, opens with a six-part instrumental unlike anything else they had recorded up to that point. It ends with "Alan's Psychedelic Breakfast," a supremely weird 13-minute instrumental largely written by Nick Mason. The band has spoken ill of this album over the years, finding it extremely dated, but it was their first Number One in England. It was the start of a very good decade.