Guitar theory question?

D and C are both in the key of G major.

G minor is the relative minor of Bb major.

So if you switch from G major (G Ionian) to G natural minor (G Aeolian) you keep the same tonic, or root note (G), but you match the chords.

G aeolian isn't the only scale you could use there, but it's one option that makes sense.

Note boat, in this situation, I am curious to know why the G Aeolian will work?

Why does the Eb not sound odd? Is it purely because it is part of the Bb major scale and you are playing it only over the Bb? and if so, even then, why doesn't it sound weird to the ears that is mainly used to the E natural played over the other two chords?

Thanks, AL

Edit: come to think of it, why doesn't the chord progression itself sound odd? Shouldn't the Bb not quite fit? :D

Yes, the Bb chord doesn't quite fit - because it has F natural, and the D major chord has F#. In situations like that, we don't change the progression, but we have to change keys and/or scales (because the Bb clashes with the B in the G major scale).

Since the first two chords set up the key of G, or the key of Em - the only two keys that have both C and D major occurring together, we have to look for an alternative. The tonic (or parallel) minor is Gm; that contains Bb.

It's true that if we play in G aeolian, the Eb may clash. I say "may", because it depends on how the line is structured. We could eliminate that conflict by using G dorian (G-A-Bb-C-D-E-F) - but the original question was what aeolian mode made sense. The other alternative might be D aeolian, relative to the key of F - but I think it makes far more structural sense to keep the tonic the same.

Besides, most people who would think "oh, I'll play in D dorian here" will have a hard time doing so, because you'd be focused on the third of the chord as your target, which is harmonically the weakest - so they may be thinking D Dorian, but they'll usually end up playing in Bb lydian! (Which is one big reason many guitarists get so confused about the use of modes). But there's very little risk of misidentifying the scale you actually use when you're going to a parallel tonic, as your ear is already honing in on G.

Thanks Noteboat :D

When I was writing my post, I did indeed think to myself, that G Dorian would be a better fit - I think that some of what you have said over the years is finally sinking into my very slow brain :D

Thanks,
Al

Just a kind of after thought:

If I were to listen to this kind of progression I would probably play in D major and treat the C as a bVII, mostly because I'm used to that sound in the type of music I play, and I'd treat the Bb as a bVI and imply the maj7 in my playing.

Sure I wouldn't play the C# in D and I'd play C and I'd be playing D Myxolydian technically, and I wouldn't play F# in the Bb so there I would be technically in D Phrygian.

My point is that I would probably focus on the D note throughout my playing and resolve to it.

What you're saying about starting in G major and switching to G minor at the Bb sounds cool, but, at least in the type of music I hear and play, I never hear a progression like that. As in V - IV - bIII

The I - bVII - bVI is way more common for me.

um thats all :)

I have the chord sequence D-C-Bflat. My guitar teacher showed me how to play scales over them as they are not in the same key. BUT i cant remember them :L. I know one was a major scale which was played over the D and C (i think) and the other was a Aeolian mode over the B flat. But which scales and why?? I hope you understand :)

Why don't you start only by playing chord tones. Just the notes of the triads. It is not an easy task if you try it in different parts of the neck. This way you can create simple melodies. When you will have control with this concept you can add scale notes. The first 2 chords belong in the same key of G Major. On the last chord you can try out F Major.