For a recording this intimate, format matters. The "FLAC" (Free Lossless Audio Codec) format is the gold standard for listeners who want to hear the performance exactly as it was captured by ECM Records producer Manfred Eicher.

What emerges is a solo improvisation so fluid, so emotionally raw, that it becomes the best-selling solo piano album of all time and the best-selling piano album in ECM’s history. Critics call it "a myth." Jarrett calls it "the most intense experience I’ve ever had."

It was a perfect storm of mishaps. Jarrett was exhausted from a long drive, suffering from back pain, and hadn’t slept. To make matters worse, the piano provided was a substandard Bösendorfer grand that was out of tune, with some keys sticking and the upper register sounding dull.

The recording of the Köln Concert was a bit serendipitous. It was made by a German radio station, WDR, without Jarrett's knowledge, and it was initially intended for radio broadcast only. The recording found its way to the audience and quickly became a legendary piece in the world of music.

He largely avoided the tinny high notes, concentrating his improvisations in the middle of the keyboard.

When you listen to this , you aren't just hearing notes; you are hearing the room.