voice vs voice part

voice and voice part both are nouns.

Word	Noun	Adjective	Verb	Adverb
voice	Yes	No	Yes	No
voice part	Yes	No	No	No

As nouns, voice part is a hyponym of voice; that is, voice part is a word with a more specific, narrower meaning than voice:

voice: the melody carried by a particular voice or instrument in polyphonic music
voice part: a part written for a singer

Other hyponyms of voice include primo, secondo, accompaniment, backup, musical accompaniment, support, bass, bass part.

voice (noun)	voice part (noun)
a means or agency by which something is expressed or communicated	a part written for a singer
the distinctive quality or pitch or condition of a person's speech
the ability to speak
the sound made by the vibration of vocal folds modified by the resonance of the vocal tract
expressing in coherent verbal form
the melody carried by a particular voice or instrument in polyphonic music
something suggestive of speech in being a medium of expression
A term used in phonetics and phonology to characterize speech sounds, with sounds described as either voiceless (unvoiced) or voiced.
a sound suggestive of a vocal utterance
an advocate who represents someone else's policy or purpose
(metonymy) a singer
(linguistics) the grammatical relation (active or passive) of the grammatical subject of a verb to the action that the verb denotes

voice (verb)	voice part (verb)
give voice to
utter with vibrating vocal chords