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.