Low sound on beat failing to generate excitement (7)
I believe the answer is:
humdrum
'failing to generate excitement' is the definition.
(humdrum means boring)
'low sound on beat' is the wordplay.
'low sound' becomes 'hum' (low-pitched sound).
'on' says to put letters next to each other.
'beat' becomes 'drum' (synonyms).
'hum'+'drum'='HUMDRUM'
(Other definitions for humdrum that I've seen before include "Mundane, commonplace" , "Droning sounds" , "Monotonous; commonplace" , "Far from exciting" , "Everyday, boring" .)