A cadence in music is a series of chords built on certain notes
(degrees) of the scale. It matters not what key you are in; the
concept remains the same. In some ways, it doesn't even matter
what type of scale you are using.... major or minor.
Scale Degrees
The note positions (degrees) in a scale are written in roman
numerals. There are seven positions because a scale has seven
notes....
I
tonic
II
super-tonic
III
mediant
IV
sub-dominant
V
dominant
VI
sub-mediant
VII
sub-tonic
So, if you were dealing with a C major scale, these would resolve as
follows:
I
tonic
C
II
super-tonic
D
III
mediant
E
IV
sub-dominant
F
V
dominant
G
VI
sub-mediant
A
VII
sub-tonic
B
Cadences
There are several commonly used cadences that remain within one key, as
follows:
Type
Chords
half
I, V
???
I,V, I
plagal
I, IV, I
full
I, IV, V, I
A full cadence in G would be: G, C, D, G A very popular
cadence in .G.
Sometimes, people tend to substitute a different chord when it's time
for the IV chord. They like to use a minor ii chord, like this
for our previous example: G, a, D, G That's a nice little
alteration from standard.
The plagal cadence is very popular with the Amen at the end of quite a
few church hymns.
This is what normally occurs with chord structure in a short piece, or
in a small section of a longer piece. After you feel comfortable
with this, you can a broader look, see the forest through the trees,
and see how larger pieces are structured. they tend to follow a
circle of fifths descend to the finish line.