How are Dorian and Aeolian different?

Question

In, e.g. the Drunken Sailor, we start the melody on a Dm chord then go down to a Cmajor chord. Well, it ends the melody on the D note but...we seem to rest a bit on C as well. It's like C is not the 7th note in the scale. How is it that the Dorian mode is not just the Aeolian mode with a non-flat sixth?

Answer 1

Thanks so much for your question! Just as you said, technically, the patterns of Dorian and Aeolian ARE the same except that Dorian's sixth is not flat. This difference, however, is astronomical in that it changes the quality of the sound, as shown by the tonal center. Say, for example, that the piece seems to be in D minor (D aeolian) with a raised sixth. This raised sixth created the same pattern as if you would move the tonal center to the second degree of the major scale. D minor has a relative major of F, so the second note would be G. The Dorian mode of a scale that appears to be in D minor, then, would be playing an F major scale, but beginning on G. The chord patterns still follow the original key of F, so the tonic would be on G minor, since G is the ii chord of F major.

The same way of thinking exists in the aeolian. Every time we start in relative minor, we are following the major scale and chord patterns, but moving to the tonic to the sixth scale degree, thus changing the quality. So you can see that chord qualities like the tonic, dominant, predominant, etc. would be altered in function, thus changing the potential of the piece.

Hope this is helpful. Feel free to reach out for additional questions. I'm always willing to dialogue about any and all music needs. Thanks!