I have a song with a part that I am wanting to play arpeggios over with the guitar. But just using the actual chord tones sounds boring to me. So I have started with an arpeggio pattern on the first chord that I am then repeating.
What I am doing is this:
The song is in E minor. On the part that starts with the G7 chord I start playing the arpeggio: A B D F# (and then up to the higher A and then back to F# and D, so just using these 4 notes). It sounds good. And then I start finding out what it is that I am doing there.
So I look at the scale chart for the E natural minor. The third chord is Gmaj7 and that is the closest to the G7 chord that I am getting in this chart. I am in Ionian mode (it says). And I am playing the 2nd, 3rd, 5th and 7th degrees of this mode in my arpeggio. Okay, so far so good.
Now I am applying this same step to the other chords.
Next chord is E-7, which is Aeolian mode, and again I play the 2, the 3, the 5 and the 7 of this mode, resulting in the notes F#, G, B and D. This sounds all fine and dandy.
But now my question.
The next chord I play is B-7. Applying the same procedure, I am now in Phrygian mode (or the fifth degree of the E natural minor scale.) The second degree is "C" but it sounds absolutely terrible! It is better to use C# instead. I play C#, D, F# and A, and it sounds cool over B-7.
So I have to break with my formula, and I am fine with doing so, but I would love to know what is going on on a more theoretical level to understand what is happening here.
Appreciate any insight you might have!