I've been listening to my two-CD set of Del Shannon a lot lately, and I noticed a couple of little things about the vocal melody in "So Long Baby."
The end of the line "Step by step you put me down" descends, and "down" has a melisma (Bb Ab F), so there's a musical representation (in two ways, actually) of the putting down.
The "hearts" in the line "We tried to break each other's hearts" also has a melisma (Eb F Eb), so the word itself is broken into syllables, mirroring the broken hearts in the lyric.
