ok long question incoming. so recently i've been trying to use numbers to notate chords instead of just using specific chord symbols to the key (like 1m7 instead of Cm7). it seems like a good idea to get a good understanding of chord progressions and also to understand the relationships and how to transpose easily and quickly. i started doing this by using the real book and just translating them on a piece of paper. but i ran into this problem again and again and i really am stuck on it for some reason. Ok, so say we're in Cmin. an Abmaj7 chord appears. if the Cmin chord is the 1m, would the Abmaj7 be the 6maj7 (the 6th note of a C minor scale) or b6maj7 (the flat 6th of a C major scale)? i'm probably overthinking this but the b6maj7 feels better to me
b6 would be the answer here. that's just how people do it. there is logic to calling it 6 but it's just not what you're gonna see people doing out in the world. the convention, for the most part, is to refer to the Ab chord as b6 in the key of C or Cmin. and 6maj would be Amaj which you'd be certainly not likely to see in Cmin but for example you'd be likely to see 6dom7 in the key of C, with a likelyhood of 2min (Dmin) after it, etc