A lot more complicated musical effect (7)
I believe the answer is:
tremolo
'musical effect' is the definition.
(I've seen this before)
'a lot more complicated' is the wordplay.
'complicated' indicates an anagram (a complex or confusing ordering of the letters).
'lot'+'more'='lotmore'
'lotmore' anagrammed gives 'TREMOLO'.
(Other definitions for tremolo that I've seen before include "effect of repeated bowing" , "Shaky effect in music" , "Wavering effect in music" , "Vibrato effect" , "Wavering note" .)