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from BWV 1080
Double and triple fugues, employing two and three subjects respectively:
- Contrapunctus 8, a 3: triple fugue with three subjects, having independent expositions
- Contrapunctus 9, a 4, alla Duodecima: double fugue, with two subjects occurring dependently and in invertible counterpoint at the twelfth
- Contrapunctus 10, a 4, alla Decima: double fugue, with two subjects occurring dependently and in invertible counterpoint at the tenth
- Contrapunctus 11, a 4: triple fugue, employing the three subjects of Contrapunctus 8 in inversion
https://en.wikipedia.org/wiki/The_Art_of_Fugue