Of sound quality (5)
But I've got no explanation for this one! Could you help me understand?
(Other definitions for sonic that I've seen before include "of noise" , "Type of boom" , "Relating to the speed of sound" , "Using waves" , "Kind of boom" .)
'of sound quality' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for tonal that I've seen before include "With conventional key and harmony" , "Using conventional keys/harmonies" , "of sound quality" , "According to musical key" , "To do with vocal or musical sound" .)