Rubato

Am/G/D/C
C/Am/F/D

Both of those are easily in the key of G, the ♭VII taken from the parallel minor. Interpreting the first progression as belonging to C would be weak as the F♮ doesn't occur, so the sub-dominant region becomes very slack, not only that but the secondary dominant on II overemphasizes the dominant region. The notes from the C major Pentatonic and the A minor pentatonic scale lacks both the F♮ and B♮, so it can easily fit into keys located on the Tonic, dominant and sub-dominant regions (C,G and F).

blastingas10

Ok, you might need to dumb that down for me

I'm stumped. It's actually in g? Damn I was off.

So now that I get my handy dandy key chart, I see that D major is not located in the C major column. And I see that all those chords are located in the G major column. I don't really understand why but I now know to use my chart and that whichever chord ends the progression doesn't mean it's in the key of that chord. But the F major isn't in the G major column, so I'm still confused as to how the whole thing is in G major.

Rubato

The F major chord in G is taken from the parallel minor (♭VII), it's often referred to as a borrowed chord, that is to say the F major belongs to G minor (natural/unraised), because G major and G minor are so closely related it's not felt as foreign to the key. The D major in C is the secondary dominant of V (V/V), it puts emphasis on the dominant, this chord is actually fairly common, but because of the lack of strength in the sub-dominant region here it actually pushes us directly into the dominant key (G major).

The sub dominant and dominant keys are very closely related to the tonic, The sub dominant shares all notes with the Tonic except for B and the Dominant shares all notes with the tonic except for F.


T-------------------C - D - E - F - G - A - B - C
SD--F - G - A - B♭- C - D - E - F - G - A - B♭- C
D-------G - A - B - C - D - E - F#- G - A - B - C


if you look at the first progression

Am-G-D-C

they contain the notes A,C,E - G,B,D - D,F#,A and C,E,G

to cancel out the Dominant region we'd need an F♮ to counteract the F#
to cancel Out the sub-dominant we'd need a B♮ to counteract the B♭

The first chord is fairly neutral, the second cancels the sub-dominant key as we'd expect G minor (G,B♭,D). Now the key could be either C or G, since the next chord contains F# and there was no F♮ to contend with it we are now pushed straight into the key of G rather than C, the progression D-C also enforces the interpretation of G being the tonal center as it makes a deceptive progression V-IV.

This explains why the ear would struggle to find C to be the tonal center, If you done the same with G you'd find it poses no risk of moving to its closest regions, with C being its sub-dominant and D it's dominant (difference between G and D is C#, C♮ of course occurring on the first chord, the second now neutral and the third canceling out C because of the F# present.

blastingas10

You just mind ****ed me a little bit. I understood a little of that.

MoonlitSunshine

Just to clarify that some pretty important terminology isn't going over your head:



The "Tonic" is the base note of the key. If the key is C (like in the image), then the tonic is C.

The "Dominant" is the 5th up from the topic, i.e., the 5th note of the key. Again using C as an example, G is the Dominant.

The "Sub-Dominant" is a 5th down from the Tonic. In the case of C, you can see that this is F, so we can deduce that it is the 4th note of the scale.

The same logic follows for the mediant and the submedient, the 3rd (E) and 6th (A) notes of the scale respectively.

When Rubato talked about Sub-dominant and Dominant keys being closely related to the Tonic, he meant that they have almost all their notes in common. Indeed, the only difference between C and F(Sub-Dom) is a B natural in C and a B flat in F, and the only difference between C and G (Dom) is an F in C and an F sharp in G. Every key has two other keys that it only differs from by one note, which just so happen to be the dominant and sub-dominants of that key. This can be easily seen in what is known as "The Circle of Fifths"



As you can see in the above. If you go a fifth up or a fifth down, you get another closely related key. The beauty of it is that you can go the whole way around in either direction and get back to where you started. If that doesn't seem to make immediate sense, try it out - it's quite satisfying to work the whole way around it.


To relate all this to what Rubato said: Because the keys of C and G are so similar (and F, incidentally), we look for pointers to figure out which key it actually is - namely the one note they differ on; F sharp (or a B flat for F).

As rubato showed, the first chord rules out none of them - they all contain A C and E, the A minor chord. the Second chord has G B natural and D, which rules out the F (because if it were in F we would expect a chord containing B flat), Finally, the Third chord is D F sharp A, which leads us right in the direction of G, as we know it's the only one of the three which fits those notes.

Does that make sense?

Of course, this is just a guideline for finding the key - many pieces may not even bother with having a central key, and might shift between keys at will - though generally they tend to modulate (change key) to a related chord - either one up or down the circle of fifths, or possibly to the Relative Minor/Major (the Minor.Major key that shares all the same notes - each major key has one (and vice versa obviously), it's A minor for C if you want to check).

The other indicator Rubato mentioned was the chords themselves. Within a Key, each Chord has a number, defined by where it sits on the scale of the key you are in. f.ex., G is the 5th note in C, so the G chord in C is denoted V, F is IV, E is III etc. etc. Because chord progressions are so important for the tone of a piece, it means that it's easy to document the "Common" chord progressions, and the chords that turn up most often in a piece. For example, III is a chord that doesn't tend to turn up that much outside of Jazz, from what I remember (because it contains 3/5/7 of the key, which is a distinctly jazzy sound). ii (some of the chords (ii, vi, vii) are written in lower case, to denote the minor-key aspects of the chord - try playing them and you'll see why) only really ever comes up as part of a sequence of chords, because it sounds odd on its own, V and IV are waay more common, especially in Pop/Rock, and are used in tandem as a cadence (the "end" of a phrase, sort of like musical punctuation) all the time. There are lots of cadences, some more widely used than others. Each one has its own unique sound - it might be a full stop, or a comma, or in the case of the Interrupted Cadence (V-vi), like someone has gone over a bump in a car and you're waiting for it to come back down. There's an old joke about how Mozart's wife used to get him out of bed in the morning by playing an interrupted cadence. He couldn't leave it like that, so he'd have to come downstairs and resolve it :P Whether or not that happened, I have no idea, and it's probably been used with pretty much every famous composer as the subject at some point...

I hope that that didn't confuse you further, and that if there was anything that wasn't making sense thus far, that this went some way to explaining it. If you already knew all that beforehand, well, good for you :P

__________________
"I found it eventually, at the bottom of a locker in a disused laboratory, with a sign on the door saying "Beware of the Leopard". Ever thought of going into Advertising?"

- Arthur Dent

blastingas10

So I have another one. The chord progression is C/G/Am/F. Is it in the key of C?

Burning Down

Yes

blastingas10

What keys could I solo in over that? I know a C major should work, but the A minor doesn't sound bad with it. Maybe because A minor is a part of the progression? I'm a little confused as to how scales in a key that is different from the progression will still work.

Dr_Rez

Why not just stick to the main key of the progression? Use the different mods within a key for your flavors.

__________________
*Best chance of losing virginity is in prison crew*
*Always Checks Credentials Crew*
*nba > nfl crew*
*Shave one of my legs to pretend its a girl in my bed crew*

MoonlitSunshine

A minor works because it is the relative minor of C (meaning it shares all the same notes, it just sounds different because of where the scale starts).

__________________
"I found it eventually, at the bottom of a locker in a disused laboratory, with a sign on the door saying "Beware of the Leopard". Ever thought of going into Advertising?"

- Arthur Dent