I've read a few threads about the same question and seem to have really missed something from music theory 101.

My question is around, for example, Cant you See by Marshall Tucker. Very simple progression, D, Cadd9 and G. D starts and ends each verse.

The key of this song is G correct, even thought starting and ending on D?

I my limited understanding, C and D are major and 1 step apart therefore must be the IV V and G must be the I.

Yet, everyone I play with solos this with D minor. Sounds fine, but seems incorrect.

D Mixolydian has all the G major notes, so that makes sense since there is such an emphasis on the D chord, but playing D minor pentatonic has the F instead of F# that is in D Mixolydian.

Am missing something obvious? Or am I correct to say the chords of D, Cadd9 and G are in fact G major in 5,4,1,5 progression and just happens the D mixolydian is probably the best scale choice?

  • 'Can't you see?' - no I can't see how soloing in Dm works. It isn't there on the track I listened to. Could have easily morphed into Sweet Home Alabama. John's answer covers it all.
    – Tim
    Commented Jan 8, 2023 at 10:25

1 Answer 1


The song is in D, not G. The phrases start and end on a D chord and the melody centers around a D melody note with a healthy dose of F#’s, which is the 3rd of the D chord. The progression is I-bVII-IV-I. The bVII is a very common non-diatonic chord. As a matter of fact there was a question about the bVII here just recently and have been many in the past.

The soloing and guitar lines on the recording are largely D major pentatonic, D-E-F#-A-B-D. You mentioned D Mixolydian, that will also work but I’m not hearing C naturals (the “signature” note of the Mixolydian scale) melodically on the recording. The C is an integral part of the harmony though as part of the Cadd9 (bVII) chord. As a matter of fact, you could even say that this song is in D Mixolydian but because of the lack of melodic C’s it’s better thought of as being in D major.

Soloing in D minor will not sound very good on this song with the exception of maybe an occasional D minor pentatonic for a bluesy effect. However they do sometimes use an F natural melodically but only over the G chord, which implies a G7 or a bluesy note in D.

EDIT: One more point I’d like to make is that you shouldn’t try and fit the chords of a song into a key to figure out a what the key is like you did. Your logic was sound in that D and C chords are part of the key of G (which also happens to be the same chords and notes as D Mixolydian BTW) but the G chord is brief and G doesn’t feel like home. Instead look at what chord the song seems to revole around, what chord feels like a resolution takes place when you play it. The notes in the melody are also a good indicator. Many songs are 100% diatonic but many also have non-diatonic chords in them. There are no stats I know of to support this but I would say it’s close the 50-50 range across all genres of music.

  • In an answer to the ♭VII question last week, this article was linked, which I found interesting: The magnificent flat-seventh
    – Theodore
    Commented Jan 9, 2023 at 16:45
  • 1
    @Theodore That was me! I think it was in comments. Commented Jan 9, 2023 at 17:27
  • thank for teaching me, this is very helpful and see that I am misapplying what I thought I understood. this explanation helps a lot...thanks!
    – Bill Smith
    Commented Jan 10, 2023 at 15:36
  • @BillSmith My pleasure. Aside from comments you can thank me or anyone on this site that provides you with a useful answer by upvoting them and accepting the answer you think best did your question justice in the future. Feel free to ask as many questions as you like as long as they are within the guidelines of acceptable questions for the site, good luck! Commented Jan 10, 2023 at 15:48

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