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Looking through each Major Key:

At position II, III, VI are MINOR chords.

At position VII, this is a DIMINISHED chord.

Looking at the C Major Key as an example, this chord progression is made up from CDEFGAB with no sharps or flats, unlike the others. My question is why are D & E, MINOR? Why are the chords in the MAJOR key like this for the positions of II, III, and VI?

  • 1
    Unfortunately, or for simplification (if you know what is what), scales and chords (which are completely different things) are named with the same name system. The "chord signature" A names the chord consisting of the tones 1, 3 and 5 of the A major scale. The "chord signature" Cm names the chord consisiting of the tones 1, 3 and 5 of the C minor scale. Because the "chords of a scale" must use only the tones of this scale, only the cords on step I, IV and V of a major scale are major chords. Example: A scale. On II we must have Bm chord, the D# of B major doesn't exist in the A major scale. – MW1971 Oct 21 '15 at 13:19
  • There is no diminished key in standard usage. I'm closing this, "unclear what you are asking". – Maika Oshikko Sakuranomiya Feb 28 at 10:44
  • @MaikaSakuranomiya I tried to preserve OP's intent in the revision; as such, I think it's more clear now. Although this might be a dupe anyway. – user45266 Apr 11 at 17:18
  • Related: music.stackexchange.com/q/79000/45266, but I don't think it's a dupe. – user45266 Apr 11 at 17:23
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When you say "Why are the key signatures in the major key like this", you are misusing the words "key signature", so let's start by explaining that.

A key is a combination of:

  • a choice of root note
  • a choice of which set of notes are available to be played

In traditional Western music -- the musical tradition in which "major" and "minor" makes sense -- a key usually consists of 7 notes out of the 12 notes in an octave. For example, C major uses C,D,E,F,G,A,B. D major uses D,E,F#,G,A,B,C#.

A major key is defined by the number of semitones between steps. C to D is 2 semitones. D to E is 2 semitones. E to F is 1 semitones. Counting up the whole scale of C major in this way, you get 2,2,1,2,2,2,1.

A minor key is defined by a different pattern of semitone steps: 2,1,2,2,2,1,2

An easy way to understand this is by trying things out at a piano. A piano keyboard is laid out according to that major key pattern -- that's why some white piano keys have black piano keys between them, and some do not.

If you can't get at a piano or a keyboard, a computer simulation is fine. All of these patterns are just as valid on other instruments -- but the pattern of black and white notes on a piano make it easier to understand.

A key signature is a way of communicating which key you are using, by telling the reader which notes to sharpen or flatten. The key signature for D major is a sharp sign at F and another at C - because in D major you never play F or C, but you do play F# and C#. The key signature for C major is no marks, because you never play any sharps or flats in that key.

Now, back to the piano keyboard.

Consider the key of C major. What defines the key, is that you're using the 7 notes C,D,E,F,G,A,B. You are not using C#,D#,F#,G#,A#.

The basic chords are triads made up of:

  • the root note of the chord
  • two notes up in the key's notes (the third)
  • another two notes up (the fifth)

Play the C triad - C,E,G - and listen. It's a major chord. As well as telling by listening, you can tell it's a major chord by counting the semitones between the first and the third. E is 4 semitones up from C.

Now play the D triad - D,F,A - and again, listen. You can hear that it's a minor chord. Count the semitones between the first and third. F is 3 semitones up from D.

Repeat this with all the other triads, and you'll find that C,F,G are major chords, and that D,E,A are minor chords.

B is special. In all those other chords, you'll notice that the 5th is 7 semitones up from the root note. However in the B triad, B,D,F, F is only 6 semitones up from B. That is what makes it a diminished chord.

To look at it another way - if you play the C major triad, then move all your fingers one white note to the right, then two of the notes go up by two semitones (C to D, G to A) and one goes up by one semitone (E to F). As you keep moving your hand to the right, the notes below each finger go up at different rates, causing you to sometimes play major chords and sometimes play minor chords.

Repeat this experiment in a different key. For example in D major, you have the notes D,E,F#,G,A,B,C# -- and don't play D#,F,G#,A#,C. Why - because that's what you get when you raise every note in the C major scale by two semitones.

You'll find that the chords that come out of the scale are the ones written in the chart you put in the question.

  • Is a 'Key' the same thing as a 'Chord Progression'? Major key chord sequence: Maj min min Maj Maj min dim These are the key signatures, they only apply to the Major keys? – Gooseberry Aug 26 '14 at 18:36
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    I can see you are very confused. I think you need to go back to the start of whatever theory book you are using, and make sure you understand each part before moving to the next part. A key is a selection of notes. A key signature is one way of notating a key. A chord progression is a sequence of chords. – slim Aug 26 '14 at 18:51
  • @user3328660 And a chord is any set of two or more notes played together. A chord is "within" or "part of" a key when it is composed of notes originating from that key. Major keys and Major chords are not strictly related concepts, nothing about Major keys means they can't have minor chords. – Matthew Read Aug 28 '14 at 14:18
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Simple explanation: If you have the C major scale: C D E F G A B If you would want to create a chord (let's say E). You would have to use the notes from this C major scale (while playing in C). As normally, a E chord has the notes E G# and B (triad). Since we don't have a G# in our C major scale (and we are playing in C!), we need to swap the G# for a G. This would give an Em chord: E G B. In general, the chords used on any major scale are always:

I major, ii minor, iii minor, IV major, V major, vi minor, vii diminished.

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In this answer I discuss what a scale is and explain how a major scale is derived. This is followed by the definition of a key with contrasting of the keys of C major and D major as examples. After which, I explain how triads (three note chords) are formed using each note of a major scale. Major, minor and diminished chords are defined. The question of why minor chords are contained in a major scale is addressed. I finish with a discussion of naming conventions for major and minor chords in a given key.

Scale -- a series of notes organized based on a formula that defines the interval between the notes. There are many different scales, each defined by a unique formula. Intervals are most commonly expressed as a multiple of "half steps" and "whole steps" between the notes that make up a scale. A half step on a piano is the interval between a white and a black key, or the interval between B and C or E and F white keys on a piano. A whole step is two half steps. The most commonly used scale is the major scale. It is based on the formula W-W-H-W-W-W-H (W=whole step, H=half step). A scale is named after it's "root note," the first note in the scale. The C major scale follows the major scale formula perfectly: C, D, E, F, G, A, B, C. This is due to the fact that there is only a half step between E&F and B&C and a whole step between the remaining notes. However, start on any note other than C, and the major scale formula can't be followed without some help. That help comes in the form of sharps/flats. These are two names for the same note (Google it). Here, we will call them sharps (represented by the symbol "#"), and these notes are represented by the black keys on a piano. A sharp is one half step higher than the "natural" note (e.g., F vs F#). Next, let's take a look at a D major scale derived from the major scale formula: D, E, F#, G, A, B, C#, D. Why the F# and C#? Again, the interval between E and F is only a half step. The major scale formula says we need a whole step between the second and third notes of the scale. F# adds a half step to F. Thus, the interval from E to F# is a whole step, as required by the formula. The interval between F# and G is one half step. This is also what the formula requires. The same logic applies with B, C#, and D with regard to the major scale formula. All the major scales are derived in this manner.

Key--A key derives from a scale. A key consists of only notes and chords derived from the notes of a scale as defined by the root note and the formula for the scale in question. Example: C major scale, where C is the root note and the major scale formula defines the notes in the scale and the resulting chords. Let's compare the C major and D major keys. There is no F# or C# in the C major scale as compared to the D major scale, so these notes are not played in the key of C major, and no chords in C major will contain these notes. In contrast, there is no F or C in the scale of D major. Therefore, these notes will not be played and will not contained in any chords in the key of D major.

Triads -- These are chords derived from the notes that make up a scale, and taken together, form a key based on the root note of the scale. Each note of a scale can be used as the first note (triad root note) to form a triad. A triad normally consists of the root note and the third and fifth note as counted up from the root note. Example: Key of C major, with C as the root note of the first triad, the triad would be C, E, G. For the next note in the C major key, D, the triad would consist of D, F, A. Now, let's take a look at the intervals between the notes in these two triads, specifically, between the root and the third note. For the triad with C as the root, there are two whole steps between C and E (C to D and D to E). Two whole steps between the root and third note in a triad is called a major third. Triads with a major third are called major chords. For the chord with the first note of D, there are only a step and a half between D and F (D to E = one step and E to F = half step). One and a half steps between the root and the third note of a triad is called a "flattened third". A triad that contains a flattened third is known as a minor chord. If one forms triads for the rest of the notes in the C major scale, you will find that the triads that start with C, F, and G have major thirds. The triads that start with D, E, and A have flattened thirds, and are consequently minor chords. This is how a major key comes to contain minor chords. In any major key, the 1st, 4th and 5th chords will be major. In the example given here, the C chord was the 1st chord and the D chord was the second chord of the C major key. The second, third, and 6th chords in any major key are minor. By convention, the chords in a key are represented by roman numerals, the major chords are represented by capital roman numerals I, IV, V, and the minors by small roman numerals ii, iii, vi. The final chord in the C major scale, with B as it's root, has a flattened third and a flattened fifth (only 6 semitones from the root instead of the normal 7). This is referred to as a diminished chord.

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There are minor scales for the same reason that there are major scales, or Blues scales, or Klezmer scales: somebody in the past found those scales useful for making what they thought was good-sounding music, and somebody else agreed and used those scales also, and taught them to students, who made even more minor, major, Blues, Klezmer scale music, and then at some point somebody make that chart you have there.

That chart is just a jumping-off point for making music with major and minor scales. It’s not a complete representation of music. It doesn’t describe the entire soundscape. In reality, there are thousands of notes in every octave, and hundreds of scales and tunings that attempt to impose some order on that chaos. The idea with the chart is you work with it until you recognize its limitations and you outgrow it, but hopefully by that time the ideas there will have helped you to develop into a better musician.

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To try to simplify what makes a major chord major and minor chord minor, is the distance of the interval example lets take the C major scale. C. D. E. F. G. A. B

Now lets make a C triad. Keys C. E. G. also known as the 1 chord in key of C .The distance from C to E Is 2. Whole steps (Referring to the frets on a guitar ) C to D is 1 whole step. And D to E is 1 whole step Equals 2 whole steps And the distance from E to G. Is 1 1/2. Steps E to F is 1/2 step and F to G. Is 1 whole step Which gives us 2 over 1 1/2

   (Major =2 over 1 1/2 ) 
   (Minor = 1 1/2. Over 2 )

Do the same thing to the D. triad the 2 chord in key of C, D to F is 1 1/2. And the distance from F to A is 2. So making it 1 1/2 over 2. Makes it a minor triad So now we have the C chord or the 1 chord Being a Major. And the D chord or 2 chord being a Minor chord. So if you went threw them all you Would see 1 chord being a major, the 2 chord Being a minor. the 3 chord a minor, 4 chord a major And 5 chord a Major, and 6 chord a minor Now doing the same thing to the 7 chord the B Chord in key of C or B triad rather The interval from C to E is 1 and a half step And the interval from E to G is also 1 and a half steps When we have intervals 1 1/2 over 1 1/2 Is a diminished chord making the 7 chord a diminished Chord.

The 3 chord or the 3rd. Is what makes a chord A major or a minor flatten the 3rd. 1 half step Makes it a minor.

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Major keys contain Minor chords to maintain the intervalic relationships of the notes which the Major key is comprised of.

Easy to deduce from chords in C Major

C Dm Em F G Am Bdim C

google: notes in D major triad

You see the 3rd of a D triad is F#. Hence the 3rd in D must be flatted to form a Dm triad to remain consistent with the intervalic relationships of C Major which has no sharps or flats.

Same is true with Em, Am, Bdim and all other chords in C Major and this also pertains to all other Major scales which consist of intervalic relationships. In fact it is true of every scale in one way or another; intervalic relationships are the "root" from which all derivations occur.

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As users above have explained, some notes in a major scale (such as the supertonic, or ii) are harmonized with minor or diminished triads because those contain the notes in that scale (so ii in C major, D, is harmonized with D-F-A instead of D-F#-A because F# is not in C major, but F is).

But what if you harmonized every note in the C major scale with a major triad, regardless of whether any of that triad's notes were in the C major scale? You might get something like this:

...Doesn't sound like your usual fare, does it?

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The interval just refers to the distance between two notes. This is the same regardless of what key you may be in. C - E is a Major Third in a minor as well as C major. You have there a list of chords and what type they are. This is not the same as the Key signature.

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