It depends on which part of the song you like and repeat.
For example, in Queen's "We Are the Champions," if you replayed the part that goes, "I've paid my dues, time after time, I've done my sentence, but committed no crime," then you like the verse the best. If you replay the part that goes "We are the champions, my friend, and we'll keep in fighting, 'til the end..." then you prefer the chorus.
If you like the overall vocals and instrumentation of a song, you might say "I like the tune" or "I love the melody in this song." If what you love about the song is the heavy drums or the drums and the bass, you'd say "This song has a great beat" or "I love the beat in this song."
Hope this helps.
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