rallentando vs music

rallentando is not a noun while music is a noun.

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

rallentando (noun)	music (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

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

rallentando (adverb)	music (adverb)
slowing down