Then this post was intended for you! During the Consecration, the priest must repeat certain prayers. How is that possible, if he is singing Adeste Fideles?
There is a LOT of abuse going on in various parishes throughout the US. Some of these 'innovative' ideas utilized during the liturgy actually render the mass INVALID. In my previous parish, I fought back ... alone! It was a gut wrenching experience but, out of concern for my fellow catholics, I took on the challenge ... and won! (Freepmail me if you want more information on the nature of the abuse.)
I STRONGLY encourage you to read this article - Is Your Mass Valid? Liturgical Abuse . It became my resource in fighting back against the abuse. Unfortunately, there were other abuses and I lacked the stamina to address each and every one of them. Please do yourself a favor and visit that link.
I should clarify. He sings that song when the consecrated host and the precious blood are raised.