Is there a way to have different songs on your iPod Touch with different fonts for each one of them? I was trying to add fonts to my iPod touch 4G to use it for the music app and notes app through Bytafont app (yes, my iPod is jailbroken).

I want to get these   on some Led Zeppelin songs

There's an existing font which includes those symbols (Led Zeppelin 2, I guess).

Can I add the font and use it only for some songs? Is there a cydia tweak for that? Or should start developing one?
No, there isn't such a tweak which allows to add them just to some songs. Only for the whole app.