Singing the Star-Spangled Banner is one the most difficult song to sing. It feels easy, because it's so familiar, but it is one and a half octave range which means you have to have a strong vocal control in order to really do justice. And not just the music but also remembering the words and since it is performed acapella, it is easy to get lost or forget the words. For anyone about to tackle this song they should spend a lot of time rehearsing and/or performing it. It is not a one shot thing.
National Anthem O, say can you see,
By the dawn's early light,
What so proudly we hailed,u
At the twilight's last gleaming?
Whose broad stripes and bright stars,
Through the perilous fight,
O'er the ramparts we watched,
Were so gallantly streaming.
And the rocket's red glare,
The bombs bursting in air,
Gave proof through the night,
That our flag was still there.
Oh say does that star spangled banner yet wave,
O'er the land of the free, and the home of the brave.