Just last week, Concordia Publishing House released Lutheran Music and Meaning.
Here is the description of this 112-page book:
Daniel Zager believes that church music is not just a contemplative background for worship, but rather, that it plays an active role in proclaiming salvation through Jesus. Even beyond the texts, there is power and meaning in the very composition of the music itself. In Lutheran Music and Meaning, dive into the theological meaning in the Lutheran liturgical church service, learning how word and music unite to boldly proclaim the Gospel. This book will encourage and educate musicians in the church, and invigorate congregation members.