Is that illegal? The underscore for the script is America, the Beautiful so I wanted to re-do the words for that song...
Well yes and no. You should also check the copyright to make sure it is okay (if you cannot find the copyright there might not be one so it should be fine), and if you note that your original is by that it should be okay.
The lyrics for America, the Beautiful were written in 1893 and put to the tune of a hymn written in 1882, so it is in the public domain, meaning you technically can change the lyrics. The bigger question, though, is what play is it that you are preforming? As a copyrighted play, it is copyrighted as a whole entity, meaning it has been done so with the understanding you would sing America, the Beautiful as written in the script. You say it is the underscore. If the lyrics aren't part of the script, then there shouldn't be a problem.
