Wavering effect in music (7)
I believe the answer is:
tremolo
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">wavering effect in music</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for tremolo that I've seen before include "Musical shake" , "Paganini's effect" , "Unsteady effect" , "Vibrato effect" , "effect of repeated bowing" .)