Chord symbols consisting of Roman numerals are used to identify triads (three note chords) built on the various degrees of the scale.
They are I, ii, iii, IV, V, vi, and vii�.
I, IV, and V are major.
ii, iii, and vi are minor.
vii� is augmented.
The beginning of a phrase should start with an I chord and progress to a IV chord or a V chord.
A chord is inverted when the bottom note is moved to the top.
The I chord can be inverted.
The soprano note will start with any tone in the I chord.
The ending of a phrase should go from a IV chord or a V chord to an I chord.
The ending soprano note will be the root tone of the I chord.
I chords are final. A IV chord and a V chord are unfinished and need to be resolved by progressing to an I chord.
I use the key of C in the following example. Similar rules would apply in any key.
In the key of C the I chord is CEG. Its first inversion is EGC and its second inversion is GCE.
The beginning soprano note could be C, E, or G and the alto and tenor notes would be the two notes not used by the soprano. The bass note would be a lower C.
In the key of C the IV chord is FAC (the root is the forth interval of C) with the second inversion CFA which is closer to CEG. This is the I chord in the key of F.
In the key of C the V chord is GBD (the root is the fifth interval of C) with the first inversion BDG which is closer to CEG. This is the I chord in the key of G.
Remember that these two chords are on either side of the C chord in the circle of fifths.
In the key of C we would generally use the G7 chord BDFG (which is inverted) but leave out the D.
Play and listen to CEG (I), CFA (inverted IV), and BFG (V-inverted G7 with the D missing).
In the key of C, the following chords would be used with the single note as indicated:
C-CEG, D-BFG, E-CEG, F-BFG, G-CEG, A-CFA, B-BFG.
CEG goes with C, E, and G.
Only A goes with CFA.
BFG (which is the G7 without the D) goes with D, F, and B.
Play and listen to the chords while playing the appropriate single note.