Triads of a Key: I, IV, V & vi.

Roman Numerals in Music

You will be noticing now that music literacy has several quirks, such as the use of Italian words to describe techniques and expression, English, German and French to describe other things, the whole process of drawing special types of dots and lines onto staves that mean different things depending on which curly sign is drawn on at the beginning, time signatures that look like someone doesn't know how to do fractions...

The confusing conventions continue with the application of Roman Numerals to describe chords of a key.

Simplest way of doing this is to transplant a table from another post (from the post about the Dominant 7th chord)

Fancy names for notes of a scale:

Degree of the Scale	Note Name	Proper Name	Roman Numeral
1	C	Tonic	I
2	D	Supertonic	ii
3	E	Mediant	iii
4	F	Subdominant	IV
5	G	Dominant	V
6	A	Submediant	vi
7	B	Leading Note	vii

(There is no 8th because it's the same as the first)

Look at that table.

First of all congratulate me on being able to code that thing. Took me back to the time where I just about failed my Higher Computing in 2004.

Second of all, look along to the Rightmost column of the table.
You'll see the Roman numerals. Three are in Capital Letters. and the remaining ones are in wee letters (or lowercase in the Queen's English).

Now. I'm going to put all that information onto a nice image where you can see it laid out on music. I like to break it right down for you and build it back up again.

Can you now see how that relates to the written notes?

The Roman Numerals are simple enough. Now the way they are used in music is to express what number a chord is within a key - like when we describe a perfect cadence as "V-I" or "5 to 1". This means it's chord number 5 of a key, where the root note is the Dominant degree of that key's scale, and and then it's chord number 1, which is the very first note, or "Tonic" degree of that scale.

So chord V in C major is the triad of G - remember how to build a triad?

(root: G, third: B, fifth: D).

Here's the scales of C, G and F major (the three keys you need to know for Higher) built into triads using the Root-Third-Fifth formula:

Don't panic!

I'm about to explain the wee circle at the end of the vii numeral.

This is because that chord becomes a diminished chord as it is affected by the key signature, and it makes the interval between the top two notes of the triad a diminished interval (which just means it gets narrower by a semitone and sounds a bit creepier).

The ones you need to know are I,IV, V and vi, in the following 

You'll see that the minor key screws the pattern up a bit. Don't worry about that. Just be aware of what the triads are and what their corresponding numeral is. It's quite easy really!

What's chord IV of F major?

What's IV? 4.

Count up 4 from F, you get to C, build the triad, C,E,G!

Simple as that.