Terrific puzzle - and thanks for the Mac shortcuts, which I can never remember. Great clues on 18A, 52A, 9D, several others. I wonder if the 1D clue would be better as the rider of Sleepy Hollow. Also, maybe 50D's clue should be "From here ____" to avoid duplicating OHCOMEON in 39A (which is really good fill). Enjoyed it a lot!
Found the bottom right really hard! Kind of devious clue for 49A for some reason. And never heard of 44A or the album. Good themeless though. Agree clue for sleepy hollow might be off? It's the horseman that's headless, not the place? Thanks!