The melodic minor scale is very useful. It fits major, minor and dominant chords. Easy to build but as always takes time to transpose to other keys; Harmonica scaler app comes handy for that.
Start from the major scale then lower the third scale degree one semitone.
C, D, E, F, G, A, B : C-major scale
C, D, Eb, F, G, A, B : C-melodic minor scale
The tradition is to use the melodic minor when ascending but not using the same scale to descend back again. Then the natural minor is used instead. See example in C below:
| ascending | descending |
|---|---|
| Melodic minor | Natural minor |
| C D E♭ F G A B | B♭ A♭ G F E♭ D C |