A concept similar to chord progressions is of course the concept of scales progressions. We may symbolize it with S1, S2, S3, S4 , where Si are scales i=1,2,3,4 etc See also post 42.
This is in articular convenient in melody improvisations. Instead of chord transitions we have scales transitions or modulations.
The transitions are convenient when Si and Si-1 have many common notes.
An example is the progression
a) S1=A minor, S2=A harmonic minor, S3=A harmonic double minor S4=A harmonic minor, S5=A minor
b) And S1=natural A minor S2=A melodic minor (Hindu) S3 =double melodic minor (Arabic) S4=A melodic minor (Hindu),S5=A natural minor.
The logic behind these two scales progressions is the next
1) The progression starts with a natural minor which is maximal in harmony in the sense that it has the maximum number of minor and major chords, and it ends with the same scale.
2) In between it proceeds to a more "chromatic" minor scale (like the harmonic minor which has the tetra-chord 1-3-1) and then this becomes stronger as it goes to the double minor (in the first case to the harmonic double minor with two tetra-chords 1-3-1) and gradually back to the simple minor and then to the natural minor
a) S1=A minor, S2=A harmonic minor, S3=A harmonic double minor S4=A harmonic minor, S5=A minor
b) And S1=natural A minor S2=A melodic minor (Hindu) S3 =double melodic minor (Arabic) S4=A melodic minor (Hindu),S5=A natural minor.
The logic behind these two scales progressions is the next
1) The progression starts with a natural minor which is maximal in harmony in the sense that it has the maximum number of minor and major chords, and it ends with the same scale.
2) In between it proceeds to a more "chromatic" minor scale (like the harmonic minor which has the tetra-chord 1-3-1) and then this becomes stronger as it goes to the double minor (in the first case to the harmonic double minor with two tetra-chords 1-3-1) and gradually back to the simple minor and then to the natural minor
Then we may improvise with melodies in these scales. As they have common root and many common notes, the change in the finger conduction on the fretboard is rather easy.
We remind here that a way to play these scales with the rule 2 notes per string are the next
Diatonic scale
Harmonic minor
Diatonic scale
Harmonic minor
Harmonic double minor
Melodic minor (Hindu)
Melodic double minor (Arabic)