I know...most of the time it's refering to synths that the melody revolves around, but any violin like instrument would apply. Here is how a typical song is broken down:
Drums or Rhym's section-
Bass drum, Snare/claps, Hi-hat, aux's (like congos), is the heart of the track/song because it keeps moving.
Sub or Bassline
bass guitar, sub synth line...helps keep the rhythm' going by following it most of the time
Harmony-
PADS, piano/key chords, ect.
Melody-
main tune, chorus or refrain that everybody will hum or sing, harmony revolves around this