Music Theory Triad Question?

because every major scale has the same pattern of whole steps and half steps, if you build a triad on any given scale degree, you can predict whether it will be major or minor.

i will use -- for a whole step and ^ for a half step

major scale: 1--2--3^4--5--6--7^1

if you start on the first note of the scale and build a triad

- the lower 3rd of the triad has to be major, because you pass over 2 whole steps: 1--(2)--3

- the upper 3rd of the triad has to be minor, because you pass over a whole and a half: 3^(4)--5

so the triad will be major.

because we started on scale degree 1, we use the roman numeral for 1, and we make it uppercase to show that it is major.

so the chord is called: I

but if you start on the 2nd note of the scale and build a triad

- the lower 3rd will be minor because you pass over a whole step and a half step: 2--3^4

- the upper 3rd will be major because you pass over two whole steps: 4--5--6

so the triad will be minor.

because we started on scale degree 2, we use the roman numeral for 2, and we make it lowercase to show that it is minor.

so the chord is called: ii

if you keep going, you will find a pattern of major minor and diminished triads that will be the same in every major key.

so when they say "as it would normally appear in the indicated key" it means its quality should be the one you would have predicted from the pattern.

in other words, they mean make a triad on top of the note they give you, using exactly the sharps flats or naturals that show up in the key they give you. (i'd just write the key sig to do it)

and then you figure out what scale degree the note they gave you is, in the key that they specify.

turn that into a roman numeral and make it upper case or lower case based on what kind of triad it was.

oh, diminished is lowercase with a small o after it: viio (except the o should be smaller and higher)

for minor keys, its more complicated because there are three kinds of minor scales!

the most "common" chords are considered to be these: i iio III iv V VI viio

most chords follow the key signature, but V and viio need to have the leading tone raised with an accidental that doesn't appear in the key signature.

or you can think like this: i iio III iv VI are from natural minor, V and viio are from harmonic minor

(... honestly, ii made with the raised 6 from melodic minor isn't really "uncommon", but this is the list i usually see )

examples:

if they said the key was F minor and gave you a G, you would spell a triad on G, so it would contain the note names G B D. you think of the key for F minor and notice it has 4 flats, so when you apply this to the triad you spelled you get G Bb Db. it is a diminished triad.

G is the 2nd note of the F scale, so you will name this triad iio

you double check and find that it is what you expect to find when you build a triad on the second note of a minor scale.

now, if they said the key was Ab major, and gave you the note G, you would again expect the notes GBD, and then you would figure out that the key sig was 4 flats, and you would apply that to the triad, making G Bb Db, the same diminished triad you found before.

but this time, you note that G is the 7th note of the Ab scale. so you name the chord viio

you double check and find that you would expect a diminished triad on the 7th degree of a major scale.

it is the exact same chord in both examples! "G diminished"

but in the first example it was *functioning* as the iio of F minor, and in the second example it is *functioning* as the viio of Ab major.

If we say that the pitch given is C and the indicated key is F major (probably indicated by a single flat in the key signature) this is how i would work it out. . .

A triad means three notes, and they are usually spaced apart in 3rds, so if C is the root, the next note would be a 3rd higher i.e. E and the final note a 3rd higher a again i.e. G.

Because C is the 5th note of the F major scale it's function is as a dominant chord (roman numeral V).

So the answer to my hypothetical question would be: triad - CEG, function - V

When it says most common minor-key harmonies it refers to the sharpened 6th and 7th degrees of the scale suggesting that chords IV and V will be major, not minor.

I hope this helps!

Cailin's answer is not totally correct. E to G is a minor third.