Just tuning and intervals

In music, unison is two or more musical parts that sound either the same pitch or pitches separated by intervals of one or more octaves, usually at the same time. Rhythmic unison is another term for homorhythm.

musical tuning based on pure intervals

Vietnamese stringed instrument

thumb|Pythagorean ditone on C thumb|Pythagorean ditone as four just perfect fifths

musical scale

mathematical characterization of the harmonic complexity of music; way of characterizing the harmony found in a piece or genre of music, or the harmonies that can be made using a particular scale