Show off your theory chops with my weekly challenge! You’ll find a new question here every Monday. Please comment to post your reply.
This week’s challenge:
This is the English carol Here We Come a-Wassailing. The refrain changes from 6/8 to 2/4, but in the original, the music is marked “dotted quarter note equals quarter note.”

But what happens if we put the indication “eighth note equals eighth note” at the time signature change? What is the name of this musical device?

Reply to post your answer, and check back on Friday, October 29th to see if you’re right!
ANSWER for 10/25/21
This is an example of metric modulation. If the eighth notes in 6/8 are the same speed as those in 2/4, then the beat becomes one-and-a-half times faster. So we encounter an increased tempo across the time signature change. In the original at top, the tempo remains the same because the basic pulse in 6/8 (dotted-quarter note) is equal to the basic pulse in 2/4 (quarter note). So the eighth notes are now slower, but the beat stays constant.
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