Chopin's mazurkas and waltzes are all in straightforward ternary or episodic form, sometimes with a coda. The mazurkas often show more folk features than many of his other works, sometimes including modal scales and harmonies and the use of drone basses. However, some also show unusual sophistication, for example Op. 63 No. 3, which includes a canon at one beat's distance, a great rarity in music.