If there are just some borrowed chords from other modes in a melody, it would suffice to just select the mode that’s most prominent, but in some songs the mode of a melody just changes altogether pretty quickly (often while retaining the same key), after just 4 or 8 measures for example. Common modal changes/combinations within a single melody seem to be minor/Phrygian, minor/Dorian, Dorian/Mixolydian and minor/Mixolydian. It would be really cool if you were allowed to assign at least two modes (and perhaps also keys) to one melody, for extra musical accuracy.
Can you show an example of a song where this would be applicable? I’m trying to comprehend what you’re conveying, and right now I’m thinking it might be convoluted, but I want a clearer picture.
In the song “Bigroom Blitz” by Scooter and Wiz Khalifa, the first part of the intro melody (starting at 0:29) is in G Dorian, while the second part of the intro melody (starting at 0:43) is in G minor (with elements of G harmonic minor mixed in, to be precise). This is just one of the countless examples of songs with such quick modal changes, but this one is actually the one that inspired me to make this post in the first place, since I feel labeling the entire melody either just Dorian or just minor simply wouldn’t be accurate.
You can add a key change in the middle of a section. Would that suffice?