# Why does a major minor modulation with the same root work (e.g. C to Cm) [duplicate]

There are very few chord changes I cannot rationalize and fit into some mode of a major scale. One of these is a major minor change with the same root (e.g. C to Cm). The C chord has c, e, and g notes. The Cm has c, eb, and g notes. There is no major scale that fits these notes. Is there a scale that can be used to riff across these chord changes with impunity or must the change be noted and respected?

This question is similar to Theory behind the change from a major chord to the same in minor but I'm not seeing an answer in that post that includes a scale that includes the notes c, eb, e, and g. What scale(s) include the notes c, eb, e, and g.

These notes make up a C(#9) chord so the question could also be asked as what scale contains all of the notes in a C(#9) chord.

• Also I don't think you're actually talking about a modulation. It seems you just want to understand a progression that uses C and Cm or something similar.
– Dom
Commented Aug 23, 2015 at 16:40
• You might want to look up "borrowed chords" as a way of analyzing this. Using the enharmonic chord (i. e. the minor with the same root if you're in major, and vice versa) is a common musical decoration. One pop tune that come to mind that uses it fairly prominently is "Heart of Glass." Commented Aug 24, 2015 at 3:45
• Why SHOULD there be one scale that can be used over two adjacent chords in a song? Commented Aug 28, 2017 at 20:54

You can never have a scale that includes an Eb and an E at the same time because that would mean two notes are derived from the same root, namely E.

That is not the definition of a scale. You can only have each note once!!!

If you said C D# E -> this would be possible but that would not leave any place for a D. So you are stuck with a one-and-a-half step there. This interval can only be found in a harmonic minor scale (between the b6 and the major7) or any of the more exotic - lets call them gypsy-scales - that can have one or several one-and-a-half step intervals.

And - there are of course a lot of variants of Blues-scales that incorporate this interval, like:
C D# E F# G A Bb C
or even scales with 6 notes only, like:
C Eb F F# G Bb C

But as you see - with these 'artificial' scales you'll soon run out of arguments about how to interpret their notes. Of course you could interpret it as:
C D# E# F# G Bb/A# C
so there would be only one note derived from each root but I guess this is a little far fetched.

But with regular diatonic scales with 7 notes you should stick to the rules!

IONIAN (major), DORIAN, PHRYGIAN, LYDIAN, MIXOLYDIAN, AEOLIAN (minor), LOCRIAN

• "You can only have each note once"... that's not really true. Think an 8 note scale (like the half-whole diminished scale). You have to duplicate at least one note to spell the scale Commented Jul 23, 2017 at 19:59
• Definitely true. But as the OP refers to diatonic C major and C minor I composed my answer with regards to his question.. And that’s why I also pointed out the difference between diatonic and ‘artificial‘ scales (like a 6 notes blues scale) and how to interpret these ;-) Same of course holds true for a 8 note scale... Commented Aug 27, 2017 at 10:40
• I'd be careful coining those scales "artificial"; some of them are not derived from the major or minor scale. Commented Aug 27, 2017 at 17:36
• That’s exactly why I put the quotation marks ;-) Commented Aug 28, 2017 at 19:41

As pointed out in @mramosch's answer, there is no standard seven-note (heptatonic) scale containing both an Eb and an E. Also note that we're not talking about modulation when we encounter the movement C to Cm (see below for the most common occurrence of this progression without modulation).

When playing a melody over the change C - Cm you want to make the difference between the two chords clear, so you need to change scales (or only use notes that both scales have in common, but that might be a bit boring).

The most common occurrence of the progression C - Cm is actually in the key of G major. It is very common to move from the IV (C) via the iv (Cm) to the I (G). This cadence works so well because the note E in the C chord moves down chromatically to the Eb of Cm, which in turn resolves to the note D of the G major chord. Once you know how it sounds you'll start hearing it almost everywhere.

If you want to play a melody over that progression, the simplest thing is to just alter the E to an Eb as soon as you move to the Cm chord. In the key of G that would mean to move from the G major scale (C lydian) to the G harmonic major scale. Another common option is to alter two notes (E->Eb, F#->F) and play the C melodic minor scale over Cm. Yet another option commonly used is to move to G natural minor (C dorian), in which case you alter three notes of the original G major scale (E->Eb, F#->F, B->Bb).

The relative key modulation would not be Cmin to CMAJ but rather C minor to Eb Major the relative Major key. This will enable you to use a couple of pivot chords that smooth out the modulations.

If you have your c minor phrase and you end the phrase on the dominant you can let it resolve with the chord c-eb-g which could either be tonic chord of c minor or sub mediant chord of Eb Major which is both perfectly fine resolutions to a dominant chord.

As you rightly point out the type of modulation you mention will be hard to resolve easily for the reasons you point out. Although I can imagine somewhere in the history of music someone did a modulation in that manner it is not a very natural modulation.

The transition between keys is just important that what you modulate to and when your two keys seem to clash it is very hard to modulate seamlessly.

• But what about the case where there is a chord change from a major to the minor of the same root (maybe modulation is not the correct word). To use an example from popular music: in Bob Dylan's "Simple Twist of Fate" the progression is D-Fm-D7-G-Gm-D-Fm-G-D-G. In this case what is happening when the progression goes from G to Gm?
– John
Commented Aug 23, 2015 at 13:57

One possible answer is E harmonic minor. E harmonic minor has all of the notes I'm looking for.

http://www.jazclass.aust.com/scales/scahar.htm

• No, it doesn't. E harmonic minor has a D#, no Eb. This might seem a little picky, but it does make a difference. Play the scale over the change C -> Cm and you'll see / hear that it doesn't work. Commented Aug 23, 2015 at 20:01

Just for clarification about the term modulation:

As a musical term it means the process of moving to another key (as TONICA) (root) by means of a chord-progression that clearly establishes the functional part (TONICA) of the new key.

Sometimes it is enough to play a DOMINANT seventh chord to establish the new TONICA of a chord that lies a perfect 4th above the DOMINANT. This can be for two beats of a bar only, or sometimes even a single 'dominant-shot' on the last quarter note of a bar is sufficient.

If you want to hear this kind of modulation in the pure classical way listen to Puccini's Madam Butterfly where he even enforces this DOMINANT functionality with a sharp 5th (#5)in the dominant 7th chord and making a whole chain of modulation as a sequence:

C(maj7) - A7/#5 -> D(maj7) - B7/#5 -> E(maj7) - C# 7/#5 etc.

Of course this goes hand in hand with the instrumentation. For these tricks he always uses the harp, because - although being a diatonic instrument like a piano, and thus having 7 notes per octave - you can re-interpret/re-tune these strings with the pedals of a harp and finally get only the notes of this augmented dominant 7th chord. Which means you can really 'harp' up and down with both hands the full range and all strings sounding loudly at the same time (arpeggio -> arp == harp).

For other modulations you need something more sophisticated than a single dominant-7th-chord. A little cadence with a SUBDOMINANT-DOMINANT-TONICA pattern like IIm - V7 - I or IV - V7 - I or even a DOUBLE-DOMINANT pattern like II7 - V7 - I

e.g. Dm - G7 - C , F - G - C or D7 - G7 - C

My personal favorite for popular music is again from the 80's Barbra Streisand Albums where they use a pattern like:

IV/V - V -> that finally leads to -> I

to establish the new tonality. Either each chord for a whole bar or the whole set two times each chord half a bar. You can modulate from absolutely any key to any other key within a bar or two. Of course the bass note which already comprises the DOMINANT functionality has to be played decidedly while the chords above change between SUBDOMINANT and DOMINANT (IV and V).

Anything else cannot be considered as a modulation but rather a shift-over...
German has a very nice word 'RÜCKUNG' for this kind of unprepared change of tonality! It essentially means move/shift something to another place!