Wavering note (7)
I believe the answer is:
tremolo
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">wavering note</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for tremolo that I've seen before include "Paganini's effect" , "Quivering musical effect" , "Wavering note" , "A vibrating effect in music" , "Wavering effect in music" .)