Be aware that adding to the length simply by taking more of the lyrics adds very little entropy. If you're trying "Oh say can you see" then it doesn't take a lot of extra bits also to try "Oh say can you see by the dawn's early light what so proudly we hailed at the twilight's last gleaming".
Similarly, extended passages of text -- even if they don't come from a restricted corpus like that of song lyrics -- have less entropy than you'd think. A smaller number of independent random words is likely to be a better tradeoff.
Similarly, extended passages of text -- even if they don't come from a restricted corpus like that of song lyrics -- have less entropy than you'd think. A smaller number of independent random words is likely to be a better tradeoff.