eleventh

Eleventh chord on C

In music or music theory an eleventh is the note eleven scale degrees from the root of a chord and also the interval between the root and the eleventh.

Since there are only seven degrees in a diatonic scale the eleventh degree is the same as the subdominant and the interval of an eleventh is a compound fourth.

An eleventh chord is a chord which contains an eleventh. Typically found in jazz, an eleventh chord will also usually include the seventh and ninth along with elements of the basic triad structure. However, since the major diatonic eleventh (for example the F on the C11 chord shown at right) would create a dissonant minor ninth interval with the third of the chord (the E), the it is rare that the eleventh chord uses all six notes in a diatonic fashion.

Because this minor ninth interval between the third and the eleventh is more problematic to the ear and to voice leading than a major ninth would be, alterations to the third or eleventh scale degrees are a common solution. When the third is lowered, a minor eleventh chord is formed with a major ninth interval between the two notes in question (e.g. C, E♭, G, B♭, D, F). Similarly, the eleventh may be raised chromatically over a major triad (e.g. to F♯ in a C major chord) to imply the Lydian mode. A less common solution to the issue is to simply omit the third in the presence of the eleventh, resulting in a chord similar to a suspended chord (sus4). However, this type of chord should almost always be notated as a suspended chord.

The eleventh chord, with the third omitted and the seventh flattened, is particularly useful in diatonic music when a composer or accompanist wishes to allow the tonic note of a key to be heard while also sounding the dominant of that key in the bass, but while not playing the second inversion of the triad on the tonic. Therefore, something similar to a perfect cadence may be attempted under a melody which does not leave the tonic note (e.g. a perfect cadence in F might require that the melody moves by step from E to F, or from G to F; whereas, if the first of the two notes is harmonized by an eleventh chord, the melody may remain on F, while the bass still plays the typical pattern of a perfect cadence i.e. dominant-tonic). The eleventh chord also expands the versatility of the dominant pedal compositional technique.

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