in the same way fans can remember the verses from 36 chambers and recite them word for word, so do the artists.
and as its been mentioned numerous times here already, artists are on tour doing these songs all the time so it stays fresh in their memory.
The wrath of God is being revealed from heaven against all the godlessness and wickedness of men who suppress the truth by their wickedness, since what may be known about God is plain to them, because God has made it plain to them. For since the creation of the world God’s invisible qualities—his eternal power and divine nature—have been clearly seen, being understood from what has been made, so that men are without excuse. (Romans 1:18-20)