As high as an elephant’s eye

Last night, I was on the F train to West 4th Street. Somewhere around East Broadway, a young woman boarded the train and sat across from me. I noticed she was reading something, but I didn’t pay much attention to her as I read my book. Shortly, I heard her start to sing–”Ooooooooooooklahoma, where the wind comes sweeping down the plain”–and I looked up again to see that was she was “reading” was sheet music.
At West 4th, I was chuckling to myself about this as I left the train, but the music seemed to follow me. I turned to look over my shoulder and I saw the woman behind me on the escalator, still singing.