chest tone vs chest voice

chest tone and chest voice both are nouns.

Word	Noun	Adjective	Verb	Adverb
chest tone	Yes	No	No	No
chest voice	Yes	No	No	No

As nouns, chest tone and chest voice are synonyms defined as:

chest tone and chest voice: the lower ranges of the voice in speaking or singing

Other synonyms of chest tone include chest register.

chest tone (noun)	chest voice (noun)
the lower ranges of the voice in speaking or singing	the lower ranges of the voice in speaking or singing