Chord music: Encyclopedia II - Chord music - Triads

Chord music - Triads

The most commonly used chords in Western music, triads are the basis of diatonic harmony, and are tertian trichords. That is, they are composed of three notes: a root note, a note which is a third above the root, and a note which is a third above that note, and therefore a fifth above the root.

Each note has a function within the chord: the note the chord is built on is called the root of the chord, the next note (a third above the root) is called the third of the chord, and the next note (a third above, again) is called the fifth of the chord. This is true of all triads, regardless of key, inversion, or quality. For example, in an F triad, F is always the root, A (sharp, natural, or flat) is always the third, and C (sharp, natural, or flat) is always the fifth.

For another example, consider an octave of the C major scale, consisting of the notes C D E F G A B C.

The triad formed using the C note as the root would consist of C (the root note of the scale), E (the third note of the scale) and G (the fifth).

Using the same scale (and thus, implicitly, the key of C major) a chord may be constructed using the D as the root note. This would be D (root), F (third), A (fifth).

It should be immediately apparent on hearing these two chords that they have a different quality to them: one which does not stem merely from the difference in pitch between their roots C and D. Examination at the piano keyboard will reveal that there are four semitones between the root and third of the chord on C, but only 3 semitones between the root and third of the chord on D (while the outer notes are still a perfect fifth apart).

This triad on C is therefore called a major triad, or major chord, since the interval from C to E is a major third. A minor chord, such as the triad on D, has a smaller interval from root to third called a minor third, and the chord is D minor.

A triad can be constructed on any note of the C major scale. These will all be either minor or major, with the exception of the triad on B, the leading-tone (the last note of the scale before returning to a C, in this case), which is diminished. See below, and the article on the Mathematics of the Western music scale.

Chord music - Inverted triads

Triads are said to be inverted when a note other than the root serves as the bass note (that is, it is the lowest note sounded). There are three positions that triads can have, two of which are inversions:

• Root position is when the chord is as described above: in ascending thirds with its root note in the bass, creating an interval of a fifth, and a third (i.e. the tonic root position is marked, "I" in a figured bass).

• First inversion is when the third of the chord is in the bass, with the fifth of the chord next above, and the root highest, creating an interval of a sixth and a third (this is marked as, "I6".).

• Second inversion is when the fifth of the chord in the bass, with the root next above, and the third of the chord highest, forming an interval of a sixth, and a fourth (This is marked "I6/4"). Second inversion is the most unstable chord position.

For one traditional system of notation for inverted chords, see figured bass. Most Western music of any sophistication makes extensive use of inversion, since without it the harmonic resources available would be severely limited. For example, a I6/4 (second inversion of the tonic) often had cadential function in early western music since scale degree 5 is in the bass.

Listen to some triads: the first three chords played are C major root position, first inversion, second inversion; then C minor root position, first inversion, second inversion.

Adapted from the Wikipedia article "Triads", under the G.N U Free Docmentation License. Please also see http://en.wikipedia.org/wiki