The standard German language is New High German, also spoken in Austria and the German parts of Switzerland and Belgium.
Pennsylvania Dutch is a conglomerate of Palatine and Hessian dialects, amalgamated with English, and cut off from the evolution of spoken standard German for more than a century.
From Luther's translation of the Bible on the language he spoke tended to become the standard literary language as it is used now.
Besides there are other German language families, as e.g. the Nether German, Frisian and so on. In the Alps they are talking Alemannic, Bavarian and so on.
My Grandfather told me: when he was a POW in WWI, they had Bavarians and Nether Germans in camp, both not speaking High German; so they had to confer in French.
For singin German dialect songs it is difficult to give advice; in the more remote areas of my home country the pronounciation differs very much from village to village, or valley to valley.
One can try to transcribe the pronounciation of a native speaker, and the next one will call it all wrong. To represent German pronounciation with English orthography seems a little bit hazardous to me, if you consider the different ways the vowels can be pronounced.
Best way: Find a native speaker and learn his Pronounciation by heart.Wilfried