head tone vs head voice

head tone and head voice both are nouns.

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

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

head tone and head voice: the higher ranges of the voice in speaking or singing; the vibrations of sung notes are felt in the head

Other synonyms of head tone include head register.

head tone (noun)	head voice (noun)
the higher ranges of the voice in speaking or singing; the vibrations of sung notes are felt in the head	the higher ranges of the voice in speaking or singing; the vibrations of sung notes are felt in the head