It's about music, which he says is born from the experiences (one or more) of love, pain, and connection to the divine:
...music’s third place of origin is in the encounter with the divine which, from the beginning, is a part of that which defines the human reality. It is this encounter of man with the totally other and the totally great that elicits even more so new ways of expression. As a matter of fact, perhaps it could be said that even in the other two areas – love and death – the divine mystery touches us and, in that sense, it is the fact of being touched by God that constitutes the origin of music, all told. I find it moving to observe how in the Psalms, for example, singing alone does not suffice: appeal is made to all instruments. In this way the hidden music of all creation – its mysterious language – is aroused. With the Psalter, in which the motifs of death and love are also operative, we find ourselves right at the origin of the sacred music of the Church of God. One can say that the quality of music depends upon the purity and the greatness of the encounter with the divine, with the experience of love and of pain. The purer and truer this experience is, the purer and greater also will be the music that is born and develops from it.
LOVE that phrase "the hidden music of all creation," and think the last line of that paragraph is worth thinking further about. The purer and greater the love, the sorrow, the contact with God, the purer the music. It suggests there can be music that is not just "bad," but rather, false.
He goes on to introduce what he says is a new idea for him -- or at least something that has recently caught his attention:
In different cultures and religions there is present a great literary corpus, great architecture, great paintings, and great sculptures. And everywhere, there is also music. But in no other cultural setting is there music of equal greatness to that which arose from the environment of the Christian faith: from Palestrina to Bach, to Handel – all the way to Mozart, Beethoven, and Bruckner. Western music is something unique that has no equal in other cultures. And this – it seems to me – should make us think.
That called to mind the "evangelization" of Japan through the works of Bach that George Weigel wrote about several years back.
Papa R. talks a little about the tension between using great choral works and an orchestra versus "actual participation." He doesn't resolve the tension, but insists that it should be nothing more than a tension, not a line to be towed to identify sides in the liturgical wars.
Then he says something perhaps odd, or at least I don't understand it. He uses the liturgies of Pope St. John Paul II as an example of what he's speaking of.
If we call to mind the liturgy celebrated by St. John Paul II on every continent, we see the full breadth of possibilities for expressing the faith in the liturgical event; we see also how the great music of the western tradition is not foreign to the liturgy but is born and developed in it. In this way, it can contribute anew to shaping the liturgy. We do not know the future of our culture and of sacred music.
I don't recall JP II actually giving much attention to the music of the liturgy as such --and in fact one of the many things the radical Traditionalists hold against him is precisely his letting bad vestments and "native" liturgical dancing and such take place at his liturgies. Maybe that's just for World Youth Day and his other masses had great music? Not sure what to make of that, except that it tells us that BXVI's love for music in the liturgy springs not from some rigid sense of what is permissible, but rather from his own pure experience of love, pain and contact with the divine.