signature tune vs tune

signature tune and tune both are nouns.

Word	Noun	Adjective	Verb	Adverb
signature tune	Yes	No	No	No
tune	Yes	No	Yes	No

As nouns, tune is a hypernym of signature tune; that is, tune is a word with a broader meaning than signature tune:

signature tune: a melody used to identify a performer or a dance band or radio/tv program
tune: a succession of notes forming a distinctive sequence

Other hypernyms of signature tune include air, line, melodic line, melodic phrase, melody, strain.

signature tune (noun)	tune (noun)
a melody used to identify a performer or a dance band or radio/tv program	the adjustment of a radio receiver or other circuit to a required frequency
	the property of producing accurately a note of a given pitch
	a succession of notes forming a distinctive sequence

signature tune (verb)	tune (verb)
	adjust the pitches of (musical instruments)
	adjust for (better) functioning