How to determine if a single note goes from being a single note to double stop into a chord. Sometimes in a song just one note could be turn into a chord. For example in the key of C lets take the note D from C major scale and and when I think about that D note it could be in D root position of a chord (D) F A (D minor) or sometimes that D note could be a 3rd in another chord B (D) F (B dim) or sometimes that D note could be a 5th in another chord G B (D) (G major) or sometimes that D notes could be a 7th in another chord E G B (D) (E m7) or sometimes that D note could be a 9th in another chord C E G B (D) (Cmaj9). The options are endless and its like that with every note of C major scale to build a chord off of.
What I learned about a three step phrase or melody is that in a V-I-IV chord progression which is dominant-tonic-sub dominant. The melody could be D-E-C-C. And in that D note could act as a root, 3rd, or 5th in another chord that we may actually be looking for to build a chord off of the note D. So lets say for instance that D note was the 5th position in a chord and that chord would look something like this G B (D) (G major). And lets say for the E note that note could act as root, 3rd, or 5th as well in another chord. Lets say we choose the E note to act in as a third note of a chord that would make the chord look something like this C (E) G (C major). Now the C note could act as a root, 3rd or 5th of any chord. Lets say the chord was placed to act like a fifth in a chord. That would look something like this F A (C) F major.
So in all we got G B (D) G major C (E) G C major and F A (C) F major. The notes that were in parenthesis were the notes that were highlighted in the as a melody note in a chord. Anyone see where Im going with this topic