All definitions by Joe Monzo unless otherwise cited consonance, consonant The blending or fusing of the two notes in an interval or the many notes in a chord into a sound that seems to be 'at rest'. It is one pole of the continuum of musical sonance , the other pole being that of dissonance .
Dissonance seems to propel harmonic progressions on towards intervals or chords which are consonant.
For many more diagrams and explanations of historical tunings, see my book . Let me know if you don't understand something.