I think of a major third as a 'brighter' kind of third than a minor third. Similarly, a major second is a brighter second than a minor second, etc. This idea

I think of a major third as a 'brighter' kind of third than a minor third. Similarly, a major second is a brighter second than a minor second, etc. This idea generalises to the idea of modal brightness: modes (scales) with more major / augmented notes are 'brighter' than modes with fewer. For example, Lydian (with its augmented fourth) is brighter than Ionian (major). Or Dorian (with its major sixth) is brighter than Aeolian. The brightest (conventional) mode is the sixth mode of harmonic major, which goes: root, augmented 2nd, major 3rd, augmented 4th, augmented 5th, major 6th, major 7th. The least bright (convential) mode is the seventh mode of harmonic minor, which goes: root, minor 2nd, minor 3rd, diminished 4th, diminished 5th, minor 6th, diminished 7th.