Nikolai Rimsky-Korsakov · section 4 of 96
Introduction
Read and hear this section in the playable edition →A chord is the simultaneous sounding of three, four or five different notes that are stacked, or can be stacked, in thirds. For example, the notes

can be arranged in thirds:

and when they sound together they form a chord.
By contrast, the notes

which cannot be arranged in thirds,

do not form a chord; sounded together they make only an incidental combination (ensemble occasionnel).
Since a chord is built of stacked thirds, its notes clearly lie a third, fifth, seventh or ninth above the lowest note, or bass. They thus form the direct arrangement, hence the name direct or fundamental chord (root position).
If, besides the intervals just named (third, fifth, seventh), we find a fourth, a second or a sixth above the bass, the new grouping of notes is called an inversion.


There are three fundamental chords:



Any simultaneous sounding of more than five notes is regarded as an incidental combination.
A chord containing a dissonant interval (a dissonant chord) requires a move to a consonance or to a consonant chord; this move is called its resolution.
A succession is a series of two or more chords. Harmony is therefore the study of how chords are connected, of incidental combinations of notes, and of their use in musical composition.