tremolo vs trembling

tremolo and trembling both are nouns.

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

As nouns, trembling is a hypernym of tremolo; that is, trembling is a word with a broader meaning than tremolo:

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

Other hypernyms of tremolo include palpitation, quiver, quivering, shakiness, shaking, vibration.

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

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