After my Panic Attack, I'd sing my A-B-C's. By the time I got to D, the 10's of thousands of people would be storming the exits with their hands covering their ears. And that would included family and friends.
This is an interesting question, but I need more details, like uh, how am I "forced"? Do I have a choice of what instrument? What are the consequences if the crowd does not like my performance...Death? Forced to undress in front of them all? You need to help me out here in order for me to help you out with a better response. (If all else fails, I would just grab the mic, and ask the crowd to follow me in a version of "Heads, shoulders, knees and toes...." Or "If You're Happy and You Know It.."
Haha, I would get an electric guitar and scream It Never Ends by Bring Me The Horizon! Haha, I can't sing, only scream =^-^= if i could sing well, it would be Don't Wanna Be Like You by Blood On The Dance Floor, or Knives And Pens by Black Veil Brides