The I, IV, and V7 Chords.
The word chord refers to multiple notes being played at the same time. It is generally not called a "chord" until at least 3 different notes are played together, but sometimes 2 notes can be called a chord as well.
There are a few basic chords that are very common in music. We could identify these by letter name, or we could identify these by how they work functionally within a key based on their scale degree. We label these using a system of Roman numerals and exponents.
Here are the three most common chords that are generally used in a major key:
- The I chord.
- Also known as the "root" or the "tonic" chord. This is the most stable chord in a key and is considered to be at rest.
- It consists of the root, the major third, and the fifth.
- Example: In the key of C Major, the C Major chord is the I chord. It consists of the notes C, E, and G.
- The IV chord.
- Also known as the "subdominant." This serves what we would call a "predominant" function, which means it is not the chord in the key with the most tension, but helps lead to this tension when desired.
- It consists of the fourth, the sixth, and the eighth (or root).
- Example: In the key of C Major, the F Major chord is the IV chord. It consists of the notes F, A, and C.
- The V7 chord.
- Also known as the "dominant seventh." This is a 4-note chord, unlike the other two (which are 3-note chords), as the fourth note helps add maximal tension, that resolves completely when followed by the I chord.
- It consists of the fifth, the seventh, the ninth (or second), and the eleventh (or fourth).
- Example: In the key of C Major, the G dominant seventh consists of the notes G, B, D, and F.