Short answers, pulled from the story.
A chord is defined as a group of notes played together for their harmonic consonance or dissonance. The most basic type of chord is a triad, which consists of three distinct notes: the root note along with intervals of a third and a fifth above the root note. While two notes sounding together are usually termed an interval, three or more tones are called a chord.
The Baroque period began in the 17th century and continued through the 18th century. This era introduced the major and minor scale based tonal system and harmony, including chord progressions and circle progressions. It was in the Baroque period that the accompaniment of melodies with chords was developed, as in figured bass, and the familiar cadences, such as perfect authentic and plagal cadences.
A 2025 analysis of 52 million chords across 680,000 songs found that G major and C major were the most commonly used chords, accounting for 24% of all chords. These were followed by D major, A major, and F major. The study also observed a decline in chord diversity over time, with songs containing fewer unique chords and a decreasing ratio of unique chords to total chords.
Roman numerals are commonly used in harmonic analysis to denote the scale step on which the chord is built. In some conventions, upper-case Roman numerals indicate major triads, such as I, IV, V, while lower-case Roman numerals indicate minor triads, such as i for a minor chord, or ii, iii and vi representing typical diatonic minor triads. Diminished triads may be represented by lower-case Roman numerals with a degree symbol, such as vii7 indicates a diminished seventh chord built on the seventh scale degree.
A suspended second chord consists of an open fifth and a major second, such as Csus2, with notes C, D, G. A suspended fourth chord consists of an open fifth and a perfect fourth, such as Csus4, with notes C, F, G. The term suspended chord refers to a chord in which the third is replaced by either the second or the fourth.