“The Blues are a simple music and I’m a simple man. But the Blues aren’t a science, the Blues can’t be broken down like mathematics. The Blues are a mystery, and mysteries are never as simple as they look!”
– BB King, interview by David Ritz [1]

Chromatic semitones          0 1 2 3 4 5 6 7 8 9 10 11 12
Minor                                  X – X X – X – X X – X – X
Pentatonic Minor                X – – X – X – X – – X – X
Blues                                  X – – X – X X X – – X – X
Pentatonic Major                X – X – X – – X – X – – X
Mixolydian                         X – X – X X – X – X X – X
Major                                 1 – 2 – 3 4 – 5 – 6 – 7 1 (8)
Major (other naming)         I – ii – iii IV – V – vi – vii I
Chromatic semitones        0 1 2 3 4 5 6 7 8 9 10 11 12