I just added this new feature:

1. The lyric

The lyric is not available, lets enter one

2. Click the edit button

You can now edit the text above the buttons

3. Enter the lyric

If you are done editing the text click save

You can undo it at any time by pressing “cancel”

4. Save the lyric

The lyric will be stored in the previous file, if that is not writable, in the default location

Or as video (slightly outdated) http://random.sarine.nl/gmpc-lyric-edit.ogv