“The Star-Spangled Banner,” our country’s national anthem, is a famously hard song to sing. Why is that? I don’t know. I’m not a music theorist; I just pay attention to when everyone starts applauding like crazy whenever someone sings the part that goes, “O’er the land of the free(eeeeeeeee).” Thankfully, Charlie Puth — a.k.a. “Professor Puth,” as he calls himself whenever he’s explaining music stuff on Instagram — graciously explains why and how in a November 30 video announcing his Super Bowl LX gig.

“Most hard-to-sing songs span just one octave range, like a low D to a high D,” Puth displays on a whiteboard, providing “Somewhere Over the Rainbow” and “Closing Time” as relevant examples. “The Star-Spangled Banner,” however, not only jumps up an octave range but also goes five notes fu

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