As an adventurer, you may get to talk to a lot of NPCs while playing. Errende, is a singing bard in Geffen, located near the lower Kafra. The rewards may not be great, but it's a good feeling when you get to help other people (or NPCs for that matter.)
Talk to the bard and ask for his name. Ask him to sing a funny song.
He'll sing for you, but then it seems that he had forgotten a few lyrics.
He asks if you'd be able to help him. Being a helpful adventurer, you agree to do so.
He'll ask you to head to Payon and look for Gunther Doubleharmony.
You'll be asking for a song with the first line, "At one, I fell in love".
Remember to tell Gunther that Minty Errende sent you.
Gunther will write the lyrics on your back, and send you off back to Errende.
Returning to Errende, you show Gunther's scribbles.
Errende reads the lyrics and said that it is a wrong version. The lyrics were no longer a love song.
Volunteer to help him find out the true lyrics of the song.
(At this point you can return to Gunther and ask who changed the song, or just tell Minty Errende that it was Kino Kitty)
He now asks you to find Kino Kitty. If he changed the lyrics, he must have known the real lyrics.
Your next itinerary would be the Monster Research Organization in Yuno (95 184).
(I recommend that you save your warp point in Juno. The quest requires you to return here later and you can just use a Butterfly Wing instead of Warping yourself from town to town. But then again, that'll be your choice.)
Marlin Putuir (the Representative) will tell you Kino Kitty left a note that he'll be off to the desert. Of course, that could only mean Kino Kitty is now in Morroc.
There is a bard is beside a young girl in Morroc, just apologize for bothering him and ask if he knows Kino Kitty
He'll tell you that he's the one you're looking for. (He's sick though, poor poor Kino..)
He further explains that he did change the lyrics, and all Eddas contain his version.
He mentions to you that if you'd like to know the real lyrics, you can check the old books.
Go back to Errende and tell him what happened, of course, you'll help him get the original lyrics,
Errende now marks your left arm with a Crescent Moon. Proceed to Yuno, and wander around to look for a bookstore.
Enter and talk to the Old Man. He will not let you read the books unless he can prove that you are a friend.
Show him your left arm, where Errende left the mark, and he'll give you access to the books.
Investigate the Old Book over and over again until you obtain the full lyrics.
Once done, return to Errende.
He'll be very happy to know the original lyrics, and sing about the Apple of Idun for you
Once he finishes the song, you obtain a small amount of experience (I think it was around 200k)