melodic line vs melody

melodic line and melody both are nouns.

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

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

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

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

melodic line (noun)	melody (noun)
a succession of notes forming a distinctive sequence	the perception of pleasant arrangements of musical notes
	a succession of notes forming a distinctive sequence