So what?

It was 50 years ago today, Miles Davis, Cannonball Adderley, John Coltrane, Bill Evans, Paul Chambers and Billy Cobb began recording "Kind of Blue," often cited as the best-selling jazz recording of all time.
Work began at Columbia Record's studio on 30th Street at 2:30 p.m. and continued until 9 p.m. that night, with a 90-minute break. They recorded "So What," "Freddie Freeloader" and "Blue in Green." A final session on April 22 captured the other two tracks, "All Blues" and "Flamenco Sketches."
One of the delights of "Kind of Blue" is its lack of perfection -- the solos are often rough, you can hear Adderly and Coltrane stumbling here and there. Ashley Kahn noted in his amazing book on the recording Davis was upset at Coltrane for soloing in G instead of D minor on "All Blues."
But what a marvelous work it is -- setting a mood unlike any other recording, so accessible and yet intriguing. The opening bass line on "So what?" so memorable -- a perfect setup for the piano and horns' response: "So what?"