Chord (music)

A chord in music consists of multiple notes played simultaneously, though two notes played simultaneously are usually called an interval. The notes used to "build" a chord are usually assigned numbers, starting with "1" to denote the "root" note, which provides the name of the chord. Flat and sharp symbols are used to alter the position in the key that given notes are drawn from by. In Western music, chords are based upon the interval of the third, whether major or minor.

There are many types of chords in Western music, including (examples all have C as the root):

• Major chord - consists of three notes with an interval of a major third followed by a minor third: 1-3-5, C-E-G
• Minor chord - the middle note is dropped one half step: 1-♭3-5, C-D#-G
• Power chord or open fifth - the "3" is dropped (common in hard rock): 1-5, C-G
• Seventh chord - adds a fourth note, which depends on the key or sound desired.
  • Major seventh chord: 1-3-5-7, C-E-G-B
  • Major-minor seventh chord: 1-3-5-♭7, C-E-G-B♭
  • Minor seventh chord: 1-♭3-5-♭7, C-E♭-G-B♭
  • Half-diminished seventh chord: 1-♭3-♭5-♭7, C-E♭-G♭-B♭
  • Fully-diminished seventh chord: 1-♭3-♭5-♭♭7, C-E♭-G♭-B♭♭
• Augmented chord - at its simplest, the fifth is raised a half step: 1-3-#5, C-E-G#
• Diminished chord - the third and fifth are both dropped one half step: 1-♭3-♭5, C-E♭-G♭
• Ninth chord - at its simplest, adds a fifth note: 1-3-5-7-9, C-E-G-B-D

At this point, chords can start to have incredibly complex structures, for instance, the ninth chord described above could be minor, augmented, diminished, have a flat seventh, have missing notes between the root and the ninth, etc.

The use of different kinds of chords (and chord progressions) is very important to the sound and feel of different styles and genres of music.