I think the answer to this riddle is Happiness?
Answer is B apexxx i did it
I would say the best answer for this question could be the Classical Period.
The answer is D) rhythm.
During the Ars Antiqua, music theory made great strides. One of the most important innovations from this time was the devlopment of a notation, or written representation in sheet music, of rhythm. Rhythm is naturally a very important element of music, and being able to represent the rhythm of a song in written form made it much easier to play it accurately without having heard it.
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