triad plays triads in the key of C on an electric piano. The triad figure shows the score. All seven notes in the scale of C major are used as roots and the lowest pitched note in each triad is the root. The piece starts and ends on the tonic triad and the chord progression is the same as in root.
A triad is a tertian chord containing three notes.
There are four types of triad:
A major triad contains a root, a major third and a perfect fifth. It is numbered with an upper case Roman numeral I to VII. The word, major, is often dropped from the chord name. The C major triad, or C triad, in the first bar of triad is CEG. It is numbered I because the root note, C, is the first degree of the scale of C major.
A minor triad contains a root, a minor third and a perfect fifth. It is numbered with a lower case Roman numeral i to vii and named minor, m for short. The Am triad in bar 2 is ACE. It is numbered vi because the root note, A, is the sixth degree of the scale of C major.
A diminished triad contains a root, a minor third and a diminished fifth. It is numbered with a lower case Roman numeral, a circle symbol is added after the number, and it is named diminished, dim for short. The Bdim triad in bar 3 is BDF. It is numbered viio because the root note, B, is the seventh degree of the scale of C major.
An augmented triad contains a root, a major third and an augmented fifth. It is numbered with an upper case Roman numeral and the symbol + added after the number. It is named augmented, aug for short. The Caug triad is CEG#. There is no augmented chord in the key of C or in any major key. In the key of A harmonic minor, the Caug triad is numbered III+ because the root note, C, is the third degree of the scale.
Chord and triad are often used interchangeably. A major triad, for instance, is often described as a major chord. The guide follows suit but differentiates a triad from other types of chord when necessary for the following reasons:
All triads are chords but not all chords are triads. A triad is a tertian chord containing three notes. A chord can contain any number of notes and any mix of intervals.
All triads contain three notes but not all three note chords are triads. In fact, most chords with three notes are not triads. For example, ABC, ABD, ABE, ABF and ABG are all not-triads, there are many more.
All chords with two notes are not triads. A dyad containing the interval of a third or a fifth or a sixth can be treated as an incomplete triad.
All chords with four or more different notes are not triads.
A triad may well be the workhorse of harmony but there are plenty of other types of chord out there for you to choose from.
