I have a song based around the Emaj - Cmaj - Dmaj chords in that order.
What key would you say this is in and what scales or modes would you use to solo over them?

C Lydian and D Mixlydian are options as C - D are the 4-5 chords from the parent G major scale. E Ionian patters also would fit. Any more suggestions?

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  • The whole piece is a repetition of those three chords? What’s the vocal melody doing? If it’s just three chords you want to improvise over (and it’s not really a song) then I’d just use the G major/E minor key signature because it probably takes the least amount of ink. Nothing really establishes a home chord here. Try improvising with B pentatonic minor: B D E F# A B. – trw Jan 23 at 0:51
  • 2
    please note that C Lydian and D Mixlydian both contain the same notes and would produce the same sound when used for improvising on this sequence – Aric Jan 23 at 2:08
  • I mean, this could be I-♭VI-♭VII, but with zero context I hesitate to answer. – user45266 Jan 23 at 4:40
  • The quick answer is 'those chords do not define a key.' That's OK. Music doesn't need to be in a key. Are you trying to figure out something else like how to notate it on staff? – Michael Curtis Jan 23 at 23:09

One might justifiably say that the E part is in E major, and the C and D parts are in E minor. Or many other things. If you want to use just one key signature marking, it could be E major. Or it could be E minor.

If you make the E an E7 at least for awhile, it nicely flirts with the coming C - D part.

Which scales? Myself, I tend to think in terms of sets of chords and a tonal center, and scales come as a byproduct that's usually not worth thinking about much. But I'll try to speak guitarese now.

I feel that this chord progression has a gradient of tonal ambiguity possibilities for soloing. On the E major, you have the largest freedom in setting the "how many sharps are there now in the scale" slider.

On the E major chord : here you have the widest selection for scales, ranging from 4 sharps to 1 sharp.

  • E major (4 sharps): if you want to say “this is not blues or rock”, outline an E maj 9 chord, after the chord progression's C - D part. Cheesy happy ending! Chords to outline: Diatonic chords from the E major key: E, F#m, G#m, A, B, C#m, D#dim. Or e.g. their sus4 or sus2 variations.
  • E mixolydian (3 sharps) : flirts with the D major chord. Chords to outline: Diatonic chords from the A major key: E, F#m, G#dim, A, Bm, C#m, D. (And their sus4 or sus2 variations)
  • E dorian (2 sharps) : does a blues/rock thing by playing a G on the chord's G#, while also keeping the door open for a D major with a C#. Chords to outline: Diatonic chords from the D major key: Em, F#m, G, A, Bm, C#dim, D. (And their sus4 or sus2 variations)
  • E minor pentatonic or E blues ("1 sharp" ... F# that you know is there like it's in E minor, but you choose not to play it) : if you come in from the C - D part and want to keep repeating the same rebellious rock pattern while landing on the E major. Chords to outline: Em, G ... boring, you must break free from the scale to outline more chords.
  • E mixolydian ♭6 (E, F#, G#, A, B, C, D) : bring in some A minor chord instead of the expected A major, while keeping E major as the tonic chord. This is a common trick in pop music. (The scale has the same notes as the A melodic minor.)

On the D major chord : slightly narrower palette at your disposal. From 3 sharps to 1 sharp. Pure E major interpretation with 4 sharps is not possible anymore, but interpretations towards fewer sharps are possible.

  • E mixolydian (3 sharps) : after staying in E minor feelings in the C - D part, suggest that the E-based chord might actually be E major... reveal it by bringing in E mixolydian’s G#. Chords to outline: Diatonic chords from the A major key: E, F#m, G#dim, A, Bm, C#m, D.
  • E dorian (2 sharps) : to move out from an E minor feeling, slightly before the E major chord comes in, bring in some E dorian’s C# note. "Oops, sorry, C major, you were a nice guy for awhile, but I'm so tempted by these other keys!" Chords to outline: Diatonic chords from the D major key: Em, F#m, G, A, Bm, C#dim, D.
  • E blues, E minor pentatonic ("1 sharp", F# is there as a silent partner, and the added blue note, Bb) : "Rebellion! They say an E major chord is coming, but I'm a tough rock guy, I will never give in."
  • E minor (1 sharp) : to make it clear that this D major is still good friends with the C major. "We will always stick together as good citizens of the E minor key, never flirt with E majors!" Chords to outline: Diatonic chords from the G major key: Em, F#dim, G, Am, Bm, C, D. And their sus4 or sus2 variations. Also try outlining a D9, D11 or D13 chord here.

On the C major chord : the narrowest selection of scales. 1 sharp. Think that you're in G major or E minor.

  • E minor (1 sharp). Chords to outline: Diatonic chords from the G major key: Em, F#dim, G, Am, Bm, C, D. And their sus4 or sus2 variations.
  • E blues, E minor pentatonic ("1 sharp" that you don't play)

What comes to chords to outline, you can of course do more complex and spread-out chords than the ones listed.

I didn't try listing diminished scales, because I feel the OP probably won't be playing them. The list of chords to outline would be interesting though.

Practice video

I used this question as a pretext for making a video and a backing track, demonstrating what the various scales might sound like, and the idea that you can switch between scales in different ways. I'm not sure if it makes sense to anyone. I'm still strongly of the opinion that chords and individual notes should be the leading decision-making device when deciding what to play. Scales just result from the decisions. Chords rule, scales follow.

A subject for another question would be, how those scales and chords could be used when creating phrases, or how to emphasize the changed notes when switching between scales, etc.


The major chords E (E + G♯ + B), C (C + E + G), and D (D + F♯ + A) do not establish a tonal center or home chord, so when they are repeated together, they are not in any particular key.

Here are the steps I took to come to that conclusion:

  • I considered E major as the key. After all, if a piece is trying to establish a tonal center and a home chord, there's no easier way to do it than to play it first. But if E is to be considered as such, we'd find other cues that point to E major. For example, we'd look for a V, V7, or vii° chord (in E major, those would be B, B7, and D♯°, respectively) to point us back to E. We don't see that. In fact, the other chords can't even be built from the E major scale. So we disqualify E major as the key.

  • I considered that C and D strongly suggest G major because, together, they are the IV and V chords. It could also suggest E minor, where they appear as the VI and VII chords. (Actually, those two chords could suggest any mode of G major.) But no matter which you choose, the E major chord is never in the mix. It's middle note—G♯—always sours that possibility. In fact, that's the note that makes the E major chord (or key or scale) major and not minor. And, of course, we'd expect to see G in G major, not G♯. So we need to disqualify G major and E minor as possibilities.

  • I considered C major and D major as possible keys. But these fall on their face for the same reason E major did: the other two chords can't be built on those scales and the V chord from those keys does not appear.

So there is no tonal center, no home chord, no key. It's OK. Not all music does. Not all music needs to. (See the @Michael Curtis comment.) This is not to say you can't have C and D chords in a piece that's in E major. They certainly could appear as borrowed chords. The same goes for an E major chord in the key of G major or E minor. But for that to be the case, you'd first need to establish that key. This progression doesn't do that.

You put a tag for "Key Signatures" in your question, so I'll address that. Strictly speaking, you can write any piece of music with any key signature, but the best candidates here are E major/C♯ minor and G major/E minor. E major has sharps on F, C, G, and D. So that would necessitate using a natural on the C, G, and D notes when they occur in the C and D chords. Plus, the key signature of E major and the first chord being E major would lead most people to assume that the piece is in E major. (That's on them, but we don't want to lead them astray on purpose, either.) So E major is probably not ideal. If we use G major/E minor, only one note needs an accidental, and that's the G♯ in the E major chord. The key signature suggests the piece may be in G major or E minor, but the first chord casts that in immediate doubt, which is a good thing. A musician who looks at the score will immediately see that they need to take a deeper look.

As for what scale to use to improvise a solo, there are at least a couple approaches. You could try to figure out a scale that works over all three chords or you could switch the scale with each chord or some of the chords. My comment suggests the former. The answer by @piiperi gives you suggestions of how to do the latter.

I chose B pentatonic minor (same notes as D pentatonic major) because all the notes (B D E F♯ A B) work over all three chords and it successfully avoids any flavor of G. G would be fine over the C and D chords, but it would clash with the G♯ in the E major chord.

You'd have to be mindful of your use of A over the E chord and F♯ over the C chord, since those are only a semitone away from notes in the respective chords, but they still work as passing tones and neither creates a major/minor ambiguity.


I suspect there's a tonal centre of E major. I, bVI, bVII, I is not a diatonic progression in any one key, but it's a pretty common one in today's music.

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