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Eleventh – Definition
An eleventh (11th) is a musical interval equal to an octave plus a perfect fourth. In chord theory, the eleventh is a common extension that adds color, tension, and harmonic richness.
What is an Eleventh?
The interval spans seventeen semitones and is equivalent to a perfect fourth played one octave higher. When chords are built by stacking thirds, the eleventh appears after the seventh and ninth, creating extended harmonies commonly used in jazz, gospel, soul, fusion, and contemporary pop.
Because the eleventh forms a strong dissonance against the chord’s major third, pianists often omit or alter the third when voicing an 11th chord, or place the eleventh in a higher register for a clearer sound.
Why is the Eleventh important for pianists?
Understanding the eleventh helps pianists create richer chord voicings and more sophisticated harmonic textures. Adding an eleventh can produce an open, spacious sound that works especially well in modern accompaniment styles.
Learning how and when to use the eleventh also improves arranging, improvisation, and chord voicing skills while avoiding muddy or overly dense harmonies.