It's GUI-tar in
"Mama Don't Allow No Guitar Playin' 'Round Here."
Arlo Guthrie says "GUI-tar" several times in
"Alice's Restaurant," too.
Definitely a regional variant, rather than a metrical infelicity.
Putting the em-PHA-sis on the wrong syl-LA-ble happens occasionally in stuff I sing in church, but now I can't remember any examples.
(Hymns with wrenched, rhyme-driven syntax are more common, and annoy me far more. I'll forgive the narrators of the carol "We Three Kings" for their tendency to speak like Yoda, because they're supposed to be foreign and exotic, but I usually sigh at the rest.)