507: WHY ANY PAIR OF NOTES OF A DIATONIC SCALE AT A DISTANCE OF A WHOLE TONE CAN BE USED AS ALTERNATING DRONES FOR ANY MELODY OF THE SCALE.

 Let su take for example, the C major scale.

Then all teh 4-voices chords are the next

Cmaj7= C E G B

Dm7=  D F A C 

Em7=  E G B D

Fmaj7= F A C E

Gmaj7= G B D F

Am7= A C E G

Bdim7= B D F A

we notice that any of the 7 chromatic pairs (all pairs of distance of a 2nd) 

C-D

D-E

F-G

G-A

A-B

B-C  (semitone)

E-F  (semitone) 

exist in ALL OF THE 7 CHORDS!

Thus by choosing any of these 4 chromatic pairs, and alternating the notes so that at the time of any chord, the drone notes exist in the underlying chord, we can drone any melody of the diatonic scale.

For each song , it does not matter which pair we use, and each pair can be used for all songs. 

Of course, when we have transposition to another scale, still another pair is needed.

Or if instead of A natural minor, we transpose to A harmonic minor (g# ) or double harmonic minor (d#, g#) , then a 3rd or a forth note is needed. E.g, (G, G#, A) fo A harmonic minor

or ( D, D#, E) also. 

If we use only 3 notes classical chords

C= C E G 

Dm=  D F A 

Em=  E G B 

F= F A C 

G= G B D 

Am= A C E 

Bdim= B D F 

We notice that all the same  pairs exist in all chords except one. 

C-D

D-E

F-G

G-A

A-B

Nevertheless, the next triads of notes exist on all 7 chords

C-D-E or B-C-D

D-E-F

E-F-G

G-A-B or F-G-A

A-B-C

In other words ALL consecutive 3-notes of the scale.