To determine which notes need flats to convert a major scale to its relative minor scale, you first identify the major scale in question.
Major scales have a specific pattern of whole and half steps, and their relative minor scales start on the 6th degree of that major scale. The notes in a relative minor scale will have the same pitch but will often differ in their accidentals.
For instance, if you want to convert a C Major scale (which consists of the notes C, D, E, F, G, A, B) to its relative A minor scale, you wouldn't have to add any flats since A minor is the natural minor (which also consists of A, B, C, D, E, F, G).
However, if you are looking for the harmonic or melodic minor scales, you would add accidentals accordingly:
- A harmonic minor has the notes: A, B, C, D, E, F, G# (add one sharp - G#).
- A melodic minor ascending has the notes: A, B, C, D, E, F#, G# (add two sharps - F# and G#) and descending reverts to natural minor (A, G, F, E, D, C, B, A).
If you provide a specific major scale, I can tell you exactly which flats or sharps need to be added to create its minor counterpart. Please let me know the scale you would like to work with!