chest tone vs chest register

chest tone and chest register both are nouns.

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

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

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

Other synonyms of chest tone include chest voice.

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