melody vs melodic line

melody and melodic line both are nouns.

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

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

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

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

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