Summary:Music is Merlin's Key
Tempo brought structure to rhyme. It gave meaning to odd phrases that Merlin tried so very hard to understand. Phrases that popped into his head since young about calling forth nature or pushing back evil.
Strict beats of music were the only things that reminded him of the time before. The faster the tempo the more violent the memory. The slower the rhythm, the more etherial the concepts. If blended certain ways his king would appear, goldeny clear.
More subtle shifts with added base and then HIS King, because the ownership was never in doubt both ways, would grab his arm and pin him. It was sometimes openly, usually not.