To play along faultlessly. Certain parts of the toy guitar light up during certain parts of the song and if you are quick enough to push the buttons you'll be in tune and make the appropriate noise. It's not guitar playing, but I wouldn't call it wholly unmusical so it has more to do with reaction time and coordination. Most real string players tend to be totally crap at it initially. I'm not damning it, but I never felt inclined to try either. You can tell my age, since pacman I really can't see a higher entertainment value of computer games and I hated pacman! Too much fidgety coordination for me, I have a hard enough time playing bass.