How are chord ratios developed exactly?

1. What makes a chord consonant?
2. How are chord built?
3. Why are chords built in thirds?
4. Are chords built on thirds?

What makes a chord consonant?

Consonant chords are, roughly speaking, made up of notes that 'sound good' together, like middle C and the G above it (an interval called a fifth). Dissonant chords are combinations that sound jarring, like middle C and the C sharp above (a minor second).

How are chord built?

Major chords are built by adding the intervals of a major third and perfect fifth above the root. The root, by the way, is the starting note of the chord (in this example our root is C). The major third interval is the distance between the root and the note four semitones above it.

Why are chords built in thirds?

Chords are made because they sound good and serve a purpose to the music they are part of. Simply put chords made of thirds sound good because of science. They sound good together because of the ratio between the frequencies of vibration among the grouped notes. They are good because they sound good.

Are chords built on thirds?

A chord does not have to be made up of thirds. A chord is by definition two or more notes heard as if sounded simultaneously. Not all chords have three notes either. There are dyads (two notes), triads (three), tetrachords (four), pentachords (five), and hexachords (six).