This lodestar 1975 set didn’t just prove that an improvised solo jazz piano record could find a mass audience; it also helped solidify the intense yet dreamy aesthetic of producer Manfred Eicher’s then-young ECM label. Jarrett lets loose a torrent of ideas on the piano, delighting even himself (which you can hear whenever he lets out one of his frequent vocalizations or foot-stomps). Whether he’s ferociously plugging away at a vamp or slowly building out a tender theme, he keeps a spellbinding intimacy central to his sound.