Quick bit of history.
Kind of Blue was recorded at at the Columbia 30th Street Studios in Manhattan, nicknamed ‘the Church’, in March and April 1959. Recorded on both a mono and a three-track stereo master making a total of four tape recorders all running at the same time, one prime recorder and one safety backup each for mono and stereo. The mono tapes have since gone missing and are still lost and the two original stereo tapes were stored in Columbia's vault for over thirty years before modern remastering took place in 1992.
It was then found that Side one of the stereo recording from the first session, So What, Freddie Freeloader and Blue in Green, had been recording at the wrong speed running one percent slow thus causing it to run a bit fast when it was played back for mastering this was corrected by the time the second session took place in April. So this means that side one of all stereo releases up until this was put right in 1992 play at slightly the wrong pitch this includes all vinyl, cassette and CD. No mono releases were affected and so are still considered the best and truest releases.
It was the sound engineer Mark Wilder who corrected this in 1992, Since the mono tapes were lost, recent mono reissues were created by mixing down the three stereo tracks into one mono track. At the same time he discovered the tape speed issue Wilder also discovered an alternate take of Flamenco Sketches included on some reissues.
I will include a detailed description of each release that I intend (in time) to review.