[Theory] Do notes in I-IV-V all come from the scale?

[johnd]

Sorry if this isn't the best sub-forum, but I'm starting to learn a bit of theory and I noticed that when playing in C-major, the chords C (I), F (IV), G (V) and Am (VI) only contain notes from the scale of C-major. I only noticed because I was tinkering on the keyboard and noticed I was only playing white notes...

Thinking about it, I think the same is true for Dm (II) and Em (III). And even for Bdim (VII - I think this is the 'normal' VII-based chord?)

I wondered if this is coincidence or is some sort of fundamental theoretical underpinning? If so, why - and [how] can I use this? Is this for instance why we typically use the chords I, minor II, minor III, IV, V, minor VI, diminished VII rather than a minor IV, major VII, etc?

[stanron]

Yes these chords are always made from notes from the scale. This is diatonic harmony, only scale notes are used. If you use notes outside the scale it is called chromatic.

You can build a chord on each note of a major scale taking the first, third and fifth note from that starting point.

So in C you get

C, Dm, Em, F, G, Am and Bdim. In the UK the convention is to number these as Roman numerals, upper case for major chords and lower case for minor chords so you get,

I, ii, iii, IV, V, vi, vii.

all made from notes in the scale.

[Paultergeist]

Essentially, yes, the chords of which you are referring can be derived from the major scale........

Consider the notes of -- as an example -- the C Major scale:

C D E F G A B C (octave)

If one takes the first, third, and fifth tones -- starting of the "C" tone -- and combines those tones, one derives a Major Triad with the C tone as the Root; in other words, a C chord:

C D E F G A B C (octave)


C, E, and G notes combined = C Major triad (C chord).

If this process is again repeated --starting now on the second tone of the C Major Scale (the D note) -- a triad (chord) is again derived:

C D E F G A B C (octave)


D, F, and A notes combined = D minor triad (Dm chord).

This process can be continued with all seven tones of the Major scale, yielded seven chords which are thus said to be harmonized from the Major scale. This is a pretty fundamental concept in music theory, and of course there is much much more, but this is a good start. Your intuition led you in a good direction. Your next exercise is to take a sheet of paper, and derive the triads of the harmonized Major scale yourself -- see how those chords are built. Understand the tonal relationships -- why do they sound as they do? Add the seventh tone (1, 3, 5, 7) to your chord construction, etc.....and it only goes on from there......

Hope that helps.

[johnd]

Thanks. Does that work exactly the way on a minor scale? e.g. if I look at A minor (since it's the relative minor of C major and has the same notes) does the same principle hold?

[stanron]

Yes, for the natural minor scale. The same chords with the same notes, but starting with A instead of C.

[rick-slo]

Buy some basic book on music theory to get your ideas on the topic organized.

[johnd]

I have one. But it's pretty dry, hence having a tutor and interacting with you fine folks.

I don't recall any book explaining WHY the typical chords are I ii iii IV V vi dim-VII, certainly not as clearly as this thread as revealed!

[Paultergeist]

Originally Posted by johnd

Thanks. Does that work exactly the way on a minor scale? e.g. if I look at A minor (since it's the relative minor of C major and has the same notes) does the same principle hold?

My answer would be that it works almost the same way on a minor scale....

There are a couple of reasons for the "almost" disclaimer:

First, there are (3) different commonly-used minor scales (natural, melodic, and harmonic). They are very, very similar to each other, but have slight differences.

Secondly, in tonal harmony -- which (in my opinion) is another way to say "what our western ears tend to like to hear" -- the V chord is nearly always a "dominant seventh" chord. Making the V chord contain a dominant sevent (sound that it sounds/functions as we expect) requires an adjustment when harmonizing the minor scale:

Using the notes of A natural minor scale:

A B C D E F G A (octave)

The "one" chord (or, more properly, the "i" chord) is:

A B C D E F G A (octave)

A, C, E, and G = the Am7 chord.

(Note that I am harmonizing to include the seventh).

And so, as before, one can take the 1, 3, 5, and 7 tones -- starting on each note of the scale in sequence -- and derive the underlying chords. When the fifth chord of the natural minor scale is harmonized, however:

A B C D E F G A B C D E F G A

We derive the notes: E, G, B, and D. This is an Em7 chord -- but remember that in most popular music, we want the V chord to be a dominant seventh (NOT a minor seventh), so the G note is raised to give E, G#, B, and D (an E7 chord, a.k.a. "E dominant seventh").

So.....one can almost straight across derive the chords from hamonizing the natural minor scale.....except one has to remember to adjust the V chord to make it a dominant seventh (V7) for most music (this is sometimes referred to as tonal harmony).

This is about as far as my as my music theory goes....

[johnd]

Ah yes. I remember my tutor was saying that playing in a minor key the dominant/V can be major OR minor quite freely... no set rule.

[rick-slo]

Originally Posted by johnd

I have one. But it's pretty dry, hence having a tutor and interacting with you fine folks.

I don't recall any book explaining WHY the typical chords are I ii iii IV V vi dim-VII, certainly not as clearly as this thread as revealed!

Must not be a good book. For an organized approach read a book.
With most any book on basic music theory it is best to work through it from front to back (one concept builds on another).
Try this one for example: http://www.amazon.com/Complete-Idiot...o+music+theory

[johnd]

I think it's a good book (http://www.amazon.co.uk/Everything-G.../dp/1884848001). I just don't think pure book learning will help me play unless every step is engrained in through playing a lot. And I understand something better if I work it out myself

[Paultergeist]

Originally Posted by johnd

...... And I understand something better if I work it out myself.

Exactly. Read a book, and you might remember the concept. Sit down with paper and pencil -- guitar in your lap -- and derive the chords yourself, and you will have far greater understanding and retention.

[johnd]

Originally Posted by Paultergeist

Exactly. Read a book, and you might remember the concept. Sit down with paper and pencil -- guitar in your lap -- and derive the chords yourself, and you will have far greater understanding and retention.

Learning chords isn't my aim though, in fact knowing chords is possibly holding me back because I just go into chord-bashing mode

But we are digressing really...

[rick-slo]

Originally Posted by johnd

I think it's a good book (http://www.amazon.co.uk/Everything-G.../dp/1884848001). I just don't think pure book learning will help me play unless every step is engrained in through playing a lot. And I understand something better if I work it out myself

Right, mostly a bunch of chords book, not a book I would be looking at to learn music theory.
Another possible book to buy http://www.amazon.com/Music-Theory-G...ory+for+guitar

[johnd]

Where were all these recommendations when I was asking for them on the forum a few months back That last one looks nice, if it's available in the UK...