falsetto vs head tone

falsetto and head tone both are nouns.

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

As nouns, head tone is a hypernym of falsetto; that is, head tone is a word with a broader meaning than falsetto:

falsetto: a male singing voice with artificially high tones in an upper register
head tone: the higher ranges of the voice in speaking or singing; the vibrations of sung notes are felt in the head

Other hypernyms of falsetto include head register, head voice.

falsetto (noun)	head tone (noun)
a male singing voice with artificially high tones in an upper register	the higher ranges of the voice in speaking or singing; the vibrations of sung notes are felt in the head

falsetto (adjective)	head tone (adjective)
artificially high; above the normal voice range