music vs rallentando

music is a noun but rallentando is not a noun.

Word	Noun	Adjective	Verb	Adverb
music	Yes	No	No	No
rallentando	No	Yes	No	Yes

music (noun)	rallentando (noun)
musical activity (singing or whistling etc.)
punishment for one's actions
any agreeable (pleasing and harmonious) sounds
(music) the sounds produced by singers or musical instruments (or reproductions of such sounds)
an artistic form of auditory communication incorporating instrumental or vocal tones in a structured and continuous manner

music (adjective)	rallentando (adjective)
	(music) gradually decreasing in tempo

music (adverb)	rallentando (adverb)
	slowing down