Chords & Harmony
Triad (music)
In music, a triad is a set of three notes (or "pitch classes") that can be stacked vertically in thirds. Triads are the most common chords in Western music. When stacked in thirds, notes produce
History#
In the late Renaissance music era, and especially during the Baroque music era (1600–1750), Western art music shifted from a more “horizontal” contrapuntal approach (in which multiple, independent melody lines were interwoven) toward progressions, which are sequences of triads. The progression approach, which was the foundation of the Baroque-era basso continuo accompaniment, required a more “vertical” approach, thus relying more heavily on the triad as the basic building block of functional harmony. The primacy of the triad in Western music was first theorized by Gioseffo Zarlino (1500s), and the term “harmonic triad” was coined by Johannes Lippius in his Synopsis musicae novae (1612).
Construction#
Triads (or any other tertian chords) are built by superimposing every other note of a diatonic scale (e.g., standard major or minor scale). For example, a C major triad uses the notes C–E–G. This spells a triad by skipping over D and F. While the interval from each note to the one above it is a third, the quality of those thirds varies depending on the quality of the triad: * major triads contain a major third and perfect fifth interval, symbolized: R 3 5 (or 0–4–7 as semitones) * minor triads contain a minor third, and perfect fifth, symbolized: R 3 5 (or 0–3–7) * diminished triads contain a minor third, and diminished fifth, symbolized: R 3 5 (or 0–3–6) * augmented triads contain a major third, and augmented fifth, symbolized: R 3 5 (or 0–4–8) The above definitions spell out the interval of each note above the root. Since triads are constructed of stacked thirds, they can be alternatively defined as follows: * major triads contain a major third with a minor third stacked above it, e.g., in the major triad C–E–G (C major), the interval C–E is major third and E–G is a minor third. * minor triads contain a minor third with a major third stacked above it, e.g., in the minor triad A–C–E (A minor), A–C is a minor third and C–E is a major third. * diminished triads contain two minor thirds stacked, e.g., B–D–F (B diminished) * augmented triads contain two major thirds stacked, e.g., D–F–A (D augmented). Triads appear in close or open positions. “When the three upper voices are as close together as possible, the spacing is described as close position or close harmony. … The other arrangements … are called open position or open harmony.”
Function#
Each triad found in a diatonic (single-scale-based) key corresponds to a particular diatonic function. Functional harmony tends to rely heavily on the primary triads: triads built on the tonic, subdominant, and dominant degrees. The roots of these triads are the first, fourth, and fifth degrees (respectively) of the diatonic scale, and the triads are accordingly symbolized I, IV, and V. Primary triads “express function clearly and unambiguously.” The other triads in diatonic keys include the supertonic, mediant, submediant, and leading-tone, whose roots are the second, third, sixth, and seventh degrees (respectively) of the diatonic scale, symbolized ii, iii, vi, and vii. They function as auxiliary or supportive triads to the primary triads.
See also#
*Upper structure triad