chest register vs chest tone

chest register and chest tone both are nouns.

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

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

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

Other synonyms of chest register include chest voice.

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