Answer: Polyphony
Explanation: Polyphony is when multiple melodic lines are simultaneously playing.
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Acoustic instruments.
Simple chord progressions such as C-F-G or Am-G.
Simple time signatures such as 3/4 or 4/4.
"Sharp" or natural keys such as C, D, E, G or A.
Simple scales such as pentatonic minor (blues), pentatonic major, major, melodic minor and mixolydian.