trembling vs tremolo

trembling and tremolo both are nouns.

Word	Noun	Adjective	Verb	Adverb
trembling	Yes	Yes	No	No
tremolo	Yes	No	No	No

As nouns, tremolo is a hyponym of trembling; that is, tremolo is a word with a more specific, narrower meaning than trembling:

trembling: a shaky motion
tremolo: (music) a tremulous effect produced by rapid repetition of a single tone or rapid alternation of two tones

Other hyponyms of trembling include tremor.

trembling (noun)	tremolo (noun)
a shaky motion	vocal vibrato especially an excessive or poorly controlled one
	(music) a tremulous effect produced by rapid repetition of a single tone or rapid alternation of two tones

trembling (adjective)	tremolo (adjective)
vibrating slightly and irregularly; as e.g. with fear or cold or like the leaves of an aspen in a breeze