Determining Key Signature of a Song

[menacingone]

If I've determined all the notes in a particular song to be (for example):

C D E F G A B

How do I know if this song is in the key of C major or A minor?

Thanks.

[daystar]

by the tonal center. Is your the song built around a C or an A ?
What type of feel does the song have? If has a bright, upbeat, major feel then it is C Ionian; on the other hand if it has a melancholy minor feel then it is A Aeolian.

[menacingone]

How can I tell whether the song is built around C or A?

The song isn't upbeat, so I'd assume its A Aeolian. This brings me to another question, if both key signatures have the same notes, how can one produce an upbeat feel, while the other produces a melancholy feel?

[ttw]

Where do the cadences fall? Especially the final part of the piece. Normally a piece in C-major will have things like G-C chords or G7-C or dm-G7-C. If the piece is in a-minor, one expects things like E-a or E7-a or b0-E70-a. I'm not sure of the case of the aeolian mode; I'm not too familiar with jazz or pop theories.

As to why major sounds "happy" or minor sounds "sad," I would claim that this is mostly cultural. One can write sad songs in a major key ("Faded Love" or some other country songs) and lots of classical music in a minor key (Brahms Hungarian Rhapsodies) doesn't really sound sad. Being cultural (or conventional) doesn't mean unreal, though. There are other opinions. You may wish to use Google to find various articles on the subject.

[Malcolm]

Short answer - each key signature will have a major scale (set of notes) and one minor scale - the notes just happen to be the same in both. One set of notes is the relative major and the other set of notes is the relative minor of those two scales. It will have one set of chords one major and one minor, i.e. the Major chords will revolve around the I IV V chords and the minor will revolve around the i iv v chords. Helps to realize each key consists of 3 major chords, 3 minor chords and one diminished chord. Which chords you pick I IV V or i iv v make the difference.
C scale = C D E F G A B C
Key of C = C, Dm, Em, F, G, Am, Bdim, C

Am scale = A B C D E F G A
Key of Am = Am, Bdim, C, Dm, Em, F, G, Am

Same chords, they just play different roles C, F & G give one sound. Am, Dm, Em give one sound.

The chords played under the notes is what gives the piece it's major or minor feel. Little hard to hear this until you actually record the chord progression and then play melody notes over the chords. Then you can hear and feel the difference. You have to actually do this to "see" the difference.

Good luck.

[JonR]

How can I tell whether the song is built around C or A?
Just to put ttw's answer in more layman's terms ;):
Either C or A will sound like a "home" note. The song will sound finished or at rest on either a C chord or an Am chord. Not both - although maybe either at different points in the song, because the key focus may change, section by section.
The very last chord of the song is most likely the key chord in any case. (The first chord is also commonly the key chord in rock and pop, but this is not always the case in jazz.)

The song isn't upbeat, so I'd assume its A Aeolian. This brings me to another question, if both key signatures have the same notes, how can one produce an upbeat feel, while the other produces a melancholy feel?Tempo, mostly. Fast = happy (in major or minor key); slow = sad (in major or minor key).
Also dynamics. Soft or gentle = sad (generally).

Major or minor keys will enhance these effects, but they won't govern them.

Tempo has the strongest impact of all. A fast minor key song is not sad, but it will sound more "intense" than a fast major key one. (The stereotypical gypsy dance tune is minor key.)
A slow major key song won't be exactly "happy", but it will sound more optimistic, wistful, less depressive and dark than a slow minor key one.

IOW, minor is "darker" - but that may not mean sadder. "Dark" can still be energetic, happy and vigorous. Major = "bright" - which can still be wistful or bittersweet.

Chord types can also make a difference. Complex harmonies tend to be less happy than simple ones. At least they add depth, which signifies thoughtfulness, which suggests introspection, in turn suggesting moodiness.
(But this is a more subtle and variable effect.)

The happiest sound is uptempo triadic harmony in a major key.
The saddest is slow, minor key, with extended (or altered) chords.
And you can increase the sad quotient by adding reverb (so it sounds like you're alone in a big dark space...;)).

[Melody S.]

I didn't read completely through all the replies, but yes, although a song being happy or sad or otherwise sounding can be cultural or have to do with speed, theory wise, it is also due to the lowered third scale degree (and sixth and seventh, depending on the type of minor scale). For example, a C minor scale would have an Eb, while a major scale with the same tonal center would have an E natural. Like others have said, there are major and minor scales with the same key signature, but if you play enough major and minor scales you should be able to hear the difference naturally (by listening to the cadences, and yes, listening for the tonal center. A lot of pieces end with a V-I, aka PAC, so if the third scale degree of the last chord sounds lowered, it's probably a minor key).
And thanks to JonR, I am now about to go find out about reverb... :)

[mogvinda]

Hi everyone. My first forum post! I know very little about music theory but have recently become quite interested.

I was reading about scales and looked at the circle of fifths and all that makes sense.

What I don't understand is, if I play the following bar repeatedly, C C G G, so two strums of C followed by two strums of G, then how can I know the key? The two notes appear together in many different scales.

[JonR]

Hi everyone. My first forum post! I know very little about music theory but have recently become quite interested.

I was reading about scales and looked at the circle of fifths and all that makes sense.

What I don't understand is, if I play the following bar repeatedly, C C G G, so two strums of C followed by two strums of G, then how can I know the key? The two notes appear together in many different scales.If you're strumming them, they're not "notes" they're "chords".
Each chord contains 3 different notes. "C" chord = C E G; "G" chord = G B D (on guitar, some of these are doubled up to fill the 6 strings).
Those 5 different notes appear in two keys: C major (C D E F G A B) and G major (G A B C D E F#).

You can tell which of those two keys you are in by stopping on either chord. Which one sounds like a proper ending? That's the key chord.
If you think either sounds OK as an ending, then it could still be either key.

A way you can confirm it as one or the other is by adding one of two other chords.
Add an F somewhere. Now it will sound more like C is "home" chord (key chord).
Or add a D somewhere. Now it will sound like G is home chord.

This is because C F and G chords are only found together in the C major key. G, C and D chords are only found together in G major.

Both chords (C and G) could also be in a couple of minor keys: A minor or E minor. These are the "relative" minors of C and G - they contain the same notes, but a different chord is "home".
This is less likely because you're not actually playing an Am or Em chord!


If you really only are playing two different notes (C and G), then yes they could be in any of 12 different keys (C, G, F, Bb, Eb, Ab, and their relative minors). You need to add more notes to identify the key.

[mogvinda]

If you're strumming them, they're not "notes" they're "chords"

Seems so obvious now.

Great answer, thanks.

[Malcolm]

You are on to something ---- You have a piece of fake chord sheet music. All it shows are chords and lyrics. You would like to improvise a melody lead break while your buddy provides chords. How do you know what key/scale to use?

Write down the names of all the chords in the piece. All you are interested in is the chord major A, B, C or minor Am, Bm, Cm or is it diminished, Adim, Bdim, Cdim or has a little 0 after the letter.

Cross out the duplications and put what is left in alphabetical order.

Get your handy dandy key chart and find the key that contains all of your chords. Not some. All. That's your key. If you know the key you know the scale as they both have the same name.

Joh talked about looking for chords that go together to confirm your key/scale is what you suspect.
A way you can confirm it as one or the other is by adding one of two other chords.
Add an F somewhere. Now it will sound more like C is "home" chord (key chord).
Or add a D somewhere. Now it will sound like G is home chord.
The more you do this the more you will recognize give-a-ways .....
If there is a natural F good bet you key is C or Am
If there is one flat - like Bb - good bet F is your key.
If there is an A7 and the next chord is D good bet that A7 was the dominant seventh in the key of D.
As there is only one diminished chord in a key - if you have one in the piece get out your key chart and see which one has that diminished chord.

What's that; you don't have a handy dandy key and scale chart. Make them and keep them handy. My point, if you are a visual learner charts will help.

Good luck

[mogvinda]

A bit off topic, anyone know of a decent guitar/music teacher in west London?

I read an article on this site on the mistakes guitarists make and one was not having formal teaching. Another was having a bad teacher.

[Malcolm]

You too are on to something. You get a good teacher by asking other guitarist who they would recommend. Just asking at a music store gets you the guy that happens to be in the back room this week. Looking for cards on bulleting boards - anyone can make a card. Looking in the Yellow Pages gets you the guy that needs students. You want the guy that has a waiting list.

Good luck.

[JonR]

A bit off topic, anyone know of a decent guitar/music teacher in west London?

I read an article on this site on the mistakes guitarists make and one was not having formal teaching. Another was having a bad teacher.Well, I'm a guitar/music teacher in west London... ;)
I'll be moving to Shoreham end of July, tho, so don't hang around...

[mogvinda]

JonR, i tried to apply your notes-in-the-chords method to the following well known chord progression:

C G D A E

The notes as I understand are:

C,C#,D,E,F#,G,G#,A,B

What scale contains all these??

[mogvinda]

oh no! i was hoping to start the autumn when work quietens down a bit.

[JonR]

JonR, i tried to apply your notes-in-the-chords method to the following well known chord progression:

C G D A E

The notes as I understand are:

C,C#,D,E,F#,G,G#,A,B

What scale contains all these??Ah ha! Don't imagine that every chord sequence has to have chords all from the same scale!
This sequence - which I recognise as Hey Joe ;) - passes through at least 2 keys.
C and G could belong to C or G major (as mentioned);
D, A and E all belong to A major;
(o ryou could argue that C, G and D all belong to G; or that G, D and A all belong to D major - IOW there's a lot of key "overlap")

But this tune is clearly in the key of E overall (because E is the main chord, the chord you would end the song on - if it didn't fade out).

The common thread that ties them all together is an E keynote. C, G and D come from the key of E minor. The sequence then moves to the key of E major, via the A chord (IV of E).

In rock, it's actually very common for a major key to use a bVII chord (D in key of E), and bIII and bVI also occur (G and C). All these 3 chords are said to be "borrowed from the parallel minor" - E minor in this case.

The sequence D-A-E is very common in the key of E. It's known as a "double plagal cadence" (but don't worry, you don't need to know that; Hendrix almost certainly didn't ;)).
The opening C and G are really the same thing as the following D and A, just a whole step higher.
And the root movement is in 4ths (down, or 5ths up).
So the whole thing hangs together logically, in various ways, ending up on an E tonic. (It's just that the logic doesn't derive from simple major key theory :rolleyes: .)

You can in fact use the E minor pentatonic or E blues scale to solo over the whole sequence. But I find it works better to treat C and G as a IV-I in G major, and D and A as a IV-I in A major (IOW, pairs of chords a whole step apart). Then treat E as a normal blues E chord.
I find I get the most "Hendrix-y" sound by using the major pent of each chord. These scales fit the chords perfectly (3 chord tones plus 2 consonant notes) and have all but 1 note in common as you move from chord to chord:
C major pent = C D E G A
G major pent = G A B D E
D major pent = D E F# A B
A major pent = A B C# E F#
E major pent = E F# G# B C#
Because there are 2 whole bars on the E, I stretch out from E major pent, combining it with E minor pent. Again, this gives the most "authentic" sound for the style.
Plus, it's good to highlight the drama of the change back to C. If you stick to Em pent right through, you lose that.