About
The M3, or major 3rd interval, is very important throughout music. It originates from a natural third (the third white key from C on a piano) and thus consists out of 2 whole notes, or 4 semitones. It produces a very happy and warm sound that you will not find in any other interval.
It is the most important interval in any major chord because it literally defines the chord as major. Instead of minor chords which have a minor third.
The major 3rd can never be used as an extended note in a chord. Nor does it's equivalent, the major tenth. This is because a third is per definition a chord-note. For example, stacking thirds in a major scale (example in C) would give a major chord: C E G. These notes are chord-notes, but any notes in between (D F A and B) can be added, or extended, notes. You might see add2, add9, or 11 in a chord symbol. But if you'd count upwards from the octave (the eight note from the tonic) the tenth would be a third and is therefor never written as extension to a chord.
Examples
Check out our playlist with examples of a major third!
