tremolo vs palpitation

tremolo and palpitation both are nouns.

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

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

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

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