The Meshumad Hazzan
This story is a Habad story and it basically goes like this. There was a Hazzan in Habad known as Reb Yechiel the Meshumad. His story was that as a young boy his entire village was wiped out by a progrom. The Poritz kept him as his own son and did not tell him that he was Jewish. The boy had no idea who his true ancestors were. As the boy grew up it became appearent he had a talent for music and was sent to a music school. At school some kids taunt him for being Jewish (there are slightly different variations here) and he has no idea why. He goes back to his “father” and he is then told what happened and eventually hooks up with Habad and becomes the Hazzan.
This entire story is not in the least bit true. First, they have letters from the Hazzan Yechiel to his (real Jewish) father. Second, in those letters he discusses his lineage so he was well aware where he came from. Third, he was never a meshumad. Instead, it seems he was the meshulach for Yeshivat Tomkhei Torah. It seems that meshulach and meshumad are close enough that people got them mixed up!? However, once the meshulach became a meshumad it was only a small leap to create an entire legend surrounding his childhood.
The full article is available here.
Additionally, it seems the niggun which the story revolves around – the one for hu’ ‘elokanu in the mussaf of Shabbat is based upon a non-Jewish one.