Let me see if I can ask this more concisely than on the other forum...
Context: I'm working on the exercises in lessons 16 and 17 of "Blues You Can Use" - playing 6ths and 3rds over the fretboard over I-IV-V chords.
The part that I'm missing: how can you tell when to play a major 6th and when to play a minor 6th? I more-or-less know when it sounds good and when it doesn't, but my fingers don't know where to go in an on-the-fly situation.
Is there a shortcut to knowing which intervals to play, or is there no way around learning all of the notes on the fretboard and learning exactly which notes are in which key?
It also kind of throws me that if you are playing 6ths in the key of A (A7-D7-E7), you play a G natural over the A7 (because of the dominant 7th), but it changes to G# over the E7 (because of the 3rd). So do you match the interval to the chord or to the key?
Thanks! Hopefully I was able to explain my confusion (that is always the trick!).