I regard very few things as heresy, but guitar accompaniment to "Star of the Bar " would be one of them. It would come out sounding like a mushy waltz.
I remember once singing Adam McNaughtan's "Cholesterol" in a singaround, and somebody (unbidden) decided to provide guitar accompaniment. That was scary, the song turned into a mushy waltz, everyone swaying from side to side ......
Sing "The Star of the Bar" unaccompanied, no matter what you think your voice sounds like.