Rock music's origins lie in the highest register (7)
I believe the answer is:
tremble
'rock' is the definition.
(thesaurus)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for tremble that I've seen before include "quail" , "Betray nerves" , "Shake involuntarily" , "Shiver, quake" , "Shake - quiver" .)