The Recovering Choir Director: Sing to the Lord, available in print from the USCCB

Aristotle posts a note from Rich Leonardi that the USCCB has released the "Sing to the Lord: Music in Divine Worship." Rich makes the important points that this document was not sent to Rome for "recognitio" and that other approved texts have true authority in the Liturgy. They are listed at this link in a useful form.