three parts. Write twice, changing the parts about [Fig. 141_a_.]

To cantus firmus _b_ write fourth species in one part, as directed in
previous lessons. [Fig. 141_b_.]

To cantus firmus _c_ write third species mixed in the other three parts.
[Fig. 139_b_.]


CANTI FIRMI

[Illustration: Fig. 142.]




LESSON XXVIII


[Illustration: Fig. 143.]


EXERCISES

To cantus firmus _a_ write the fourth species in one part, as usual.

To cantus firmus _b_ write first, second and fourth species in the other
three parts. [Fig. 143_a_.]

To cantus firmus _c_ write the first, third and fourth species in the other