there are several “sung” versions of the Mystery of Faith, and Lamb of God that are approved, just make sure the one being used is approved. Just because you never heard it before does not make it wrong. There are several responsorial psalms and responses that may be used in Advent, or on feast of Mary, and may be subsituted for the one in the missalette. by the way, the missalette is not the final authority on what is liturgically correct and what isn’t. Our priest has to change or disregard a lot of what is in the missalette. We just bought the least objectionable one on the market that meets our need, and work around it.
Please do not waste the bishop’s time with a protest until you have done your homework, as suggested above.
First, simply ask the priest for clarification in a non-confrontational, non-combative way.
Second, find out if what you heard or saw is truly an abuse. This requires a lot of education and research, and is very time-consuming. Abuses are not based on your sentimental rembrance of childhood liturgy experience, or on what was done in your last parish. There are firm directives, available to any serious Catholic who wants to do the research.
third, if you truly see a serious liturgical abuse, get times, dates, facts, names and if the parish priest cannot satisfactorily explain the situation, and you do decide to go to the bishop, be factual. hearsay and generalities will not give him anything useful. Put it in writing, be prepared to back it up.