4ths and fifths are used in most standard systems of music. Actually it's just fifths because fourths are just fifths. And fifths sound good because of physic

4ths and fifths are used in most standard systems of music. Actually it's just fifths because fourths are just fifths. And fifths sound good because of physics. For example the pentatonic scale used in a lot of eastern music is subsumed by the western scale.