What does it mean to modulate?
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a. bring back the same words with the same melody at regular intervals.
b. conduct the instruments to play the same notes sung by the chorus.
c. have each voice "imitate" one another.
d. move to a different key area.

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this is for my music class in the baroque era, and i just cannot, cannot figure this question out for the life of me. me find the correct answer!
much love!