melodic line vs tune

melodic line and tune both are nouns.

Word	Noun	Adjective	Verb	Adverb
melodic line	Yes	No	No	No
tune	Yes	No	Yes	No

As nouns, melodic line and tune are synonyms defined as:

melodic line and tune: a succession of notes forming a distinctive sequence

Other synonyms of melodic line include air, line, melodic phrase, melody, strain.

melodic line (noun)	tune (noun)
a succession of notes forming a distinctive sequence	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

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