Editing lyrics

You need to enter edit mode before being able to edit lyrics in Lyricus. Enter edit mode by pressing ⌘E or clicking Edit > "Enter Edit Mode".
Once in edit mode, signified by a different background color and the text "EDITING:" in the window title, you are free to change the text.

When you are done, you can save by pressing ⌘S or clicking File > "Save lyrics", or simply exit edit mode by pressing ⌘E again.
If you don't save, Lyricus will ask whether to discard changes or save just before the display will change to another song.