tremolo vs shakiness

tremolo and shakiness both are nouns.

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

As nouns, shakiness is a hypernym of tremolo; that is, shakiness 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
shakiness: a shaky motion

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

tremolo (noun)	shakiness (noun)
vocal vibrato especially an excessive or poorly controlled one	the quality of being unstable and insecure
(music) a tremulous effect produced by rapid repetition of a single tone or rapid alternation of two tones	a shaky motion