Mile Davis and his bands is attributed with the mystery-miracle of many hours "a capella" improvisation in concerts and disc recordings.
A careful analysis reveals why this "miracle" occurs.
We will start with the very well known similar "miracle" of many hours of "a capella" meditational improvisation within a single diatonic scale.and a single monotone tonal chord, and we will reduce the Mile Davis Bands miracle to this. We only have to substitute the singlle diatonic scale with a ingle bebop 9-notes scale.
A single 8-notes bebop scale=the union of 2 diatonic scales in harmonic relation (an interval of 4th apart).
E.g. G-C.
A single 9-notes bebop scale=the union of 3 diatonic scales in harmonic relation (an interval of 4th apart).
E.g. G-C-F.
Now if e.g. C has a s tonal chord, the C major, then a 9-notes bebop scale has "tonal chord", in teh example before, teh 3 major chords are G, C, F, which are also the chords used in 12 bars blues say in C major scale. But the practice of soloing in 12 bars blues in C major, resulted in soloing in the 3 diatonic scales G, C , F , or in the corresponding single 9-notes bebop scale. This exlains why the evolution of jazz and blues resulted in 9 notes bebop scales.
Then the next 6 characteristscs of the improvisations of Mile-davies bands explain the rest
1) Mile Davis bands improvisation is a minimalistic improvisation. In other words, the number of notes is small compared to the number of rythmic beats. This makes it a slow, cool, and relatively relaxing, and pleasant music in the background.
2) There are not really chords (it is not a chord-based improvisation as e.g. in the Gypsy jazz).
Even the piano is playing mainly solos. This gives more freedom. The background is only the drums
and the bass, which essentially goes step-wise and rhythmically up and down a single 9-notes bebop scale. A Mile davis band typicaly is 5 members. The drums, the bass, piano, a trumpet and possibly a saxophone
3) Each of the 3 members who may improvise by solos (piano, trumpet, saxophone) is most ofteh times in turn and not simulteneously as in the classical New Orleans jazz.
4) The solo, in a stable way maninly in a single 9-notes bebop scale!
5) The final experience si a group meditation of 5 muscicians , that their brains produce gamma bran waves.
