Excellent puzzle with some great clues, Elfman. When 38a clicked, I had a laugh. Having cottoned on to the first set of thematics, I initially pursued another, more recent song (which one of its alleged writers thought rather poorly of). But the pdm on the second set (which produced another laugh) put me on the right track.
Google warning: more than one page which appeared at the top of searches contained a misspelling of the second writer’s name.
Do persevere with it, folks; it’s well worth it.