rhythm vs musical time

rhythm and musical time both are nouns.

Word	Noun	Adjective	Verb	Adverb
rhythm	Yes	No	No	No
musical time	Yes	No	No	No

As nouns, musical time is a hypernym of rhythm; that is, musical time is a word with a broader meaning than rhythm:

rhythm (noun)	musical time (noun)
natural family planning in which ovulation is assumed to occur 14 days before the onset of a period (the fertile period would be assumed to extend from day 10 through day 18 of her cycle)	(music) the beat of musical rhythm
recurring at regular intervals
(architecture) the repetitive use of a group of visual elements to establish a recognizable pattern
the arrangement of spoken words alternating stressed and unstressed elements
the basic rhythmic unit in a piece of music
an interval during which a recurring sequence of events occurs