I found the PERFECT song for Brock to sing in the "English" version of "Heroes of Legend" after they defeat Kyrene in the real world for the first time: the oldie "On Broadway" (in the "Japanese" version, this would just be a long guitar and scat solo with plenty of dancing)
Here's how that scene would play out:
Andra: Come on, everybody! clap your hands! ::claps along to the beat as Brock appears in a spotlight, strumming to the music::
Damien: All right! Sing it, Brock!
They say the neon lights are bright on Broadway...
They say there's always magic in the air ...
But when you're walkin' down that street,
And you ain't had enough to eat,
The glitter rubs right off and you're nowhere!
They say the ladies treat you fine on Broadway
But looking at them just gives me the blues
'Cause how ya gonna make some time,
When all you got is one thin dime?
And one thin dime won't even shine your shoes!
Hmmm....
They say that I won't last too long on Broadway...
I'll catch a great big bus for home, they all say...
But they're dead wrong, I know they are!
'Cause I can play this here guitar!
And I won't quit till I'm a star on Broadway!
::long scat solo, he's scatting along to his playing guitar, Ash and co. dance in the background, before long, even Kyrene and her minions can't stop dancing!:: (for the record, scat is a kind of jazz singing that is meant to imitate a musical instrument)
They say that I won't last too long on Broadway...
I'll catch a great big bus for home, they all say...
But they're dead wrong, I know they are!
'Cause I can play this here guitar!
And I won't quit till I'm a star on Broadway!
::more scatting::