I get what seems to be all pitches played at once. Here’s an example of what the harmony variable could be: [[[50, 48, 45], 2.5], [[54, 49, 53], 2.75], [[43, 48, 47], 5], [[62, 64, 58], 3.75], [[73, 70, 71], 4.5]]
The problem looks like the blocking=False. Only use that when you want things to be played at the same time! play_chord automatically superimposes the notes of the chord.