The clarification is that we sing the liturgy vs. sing at the liturgy.
Priests and liturgical music leaders will want to check the United States Catholic Conference of Bishops' web page at this link here. You will find sample pages of the revised Roman Missal at the links on the right side of the page. Make sure you check the USCCB on you-tube and the video page for more catechetical explanations.
Finally, check Fr. Michael Joncas' presentation on the Roman Missal on the web page from Notre Dame Center for Liturgy. Other links:
Centers and Organizations
The Association of Consultants for Liturgical SpaceThe Catholic Academy of Liturgy
Center for Liturgy at St. Louis University
Church Musician Association of America
Federation of Diocesan Liturgical Commissions
The Georgetown Center for Liturgy
The Liturgical Conference
The Liturgical Institute, University of St. Mary of the Lake
Institute for Liturgical Ministry, Dayton, OH
National Association of Pastoral Musicians
North American Academy of Liturgy
The North American Forum on the Catechumenate
The Pastoral Preaching Resource
The Society for Catholic Liturgy
Societas liturgica
The Southwest Liturgical Conference
