Not having a good singing voice suggest to me that you do at least have SOME singing ability.
So be assured that you will shine in this unfortunate cast of tone-deaf misfits.
Mrs Grundy has a lead role mainly because of throwing her considerable weight around. She sound like a startled hyena.
And the Captain.... an interesting case that sounds like like gravel stirred (not shaken) in a tin can .... though his words are interspersed with grunts and hiccups that are more melodious.
