In many parishes where the Novus Ordo is celebrated the moment of the "Sign of Peace" or "Passing of the Peace" is an occasion of grave abuses. Often the passing of the peace becomes an occasion for an unseemly familiarity or casualness which is inappropriate for the liturgy of the Eucharist. This problem is so endemic that the Vatican, following the 2005 Synod of Bishops on the Eucharist, spent years studying whether or not the Rite of Peace should be moved so as to maintain the dignity of the Eucharistic liturgy.
In one of our other liturgical quod libets we looked at the problem of the congregation going out of the way to extend the sign of peace to persons other than their immediate neighbors. This time, we look at another common question: Whether or not it is fitting for there to be a special "song of peace" sung or performed during the passing of the peace. This practice is very, very common in Catholic parishes - at the passing of the peace there is a special song performed by the "band" or choir.
In a recent circular letter issued by the Congregation for the Divine Worship and Discipline of the Sacraments , Cardinal Canizares Llovera stated that the "song of peace" or a "song for peace" is to be considered an "abuse." The document uses very strong language on this point, stating that the justification for such a song of peace is "non-existent in the Roman Rite." The letter explains that "a song for peace is not foreseen by tradition because only the briefest time is envisaged for the exchange of peace to those who are nearest." 
Introducing a "song of peace" is part of the larger train of abuses surrounding the Passing of the Peace, which all tend to inflate the importance of what is meant to be a very brief ritual. This has the effect of introducing disharmony into what the Church envisions as a very dignified and solemn Eucharistic liturgy.
 Circular Letter on the Ritual Expression of the Gift of Peace at Mass
 ibid., 6,c and footnote 9