Contemporary Catholic views on music in the Church: is music for God or for the people? I'm a non-believer church organist; I just moved to Spain and it's my first time playing regularly for a church service -- this one is Catholic.

I want to understand why Catholics have music in the church services: is it for God, or for the people? This question seems crucial to me, because as I get more creative with the music, with the organ stops / embellishments / polyphony, I want to understand what do Catholics believe about who is ultimately judging my music, them or God.

Being a non-believer, I don't really want to get into details of theology with the priest (he knows I'm a non-believer who is baptized Eastern Orthodox, and that was fine by him), so I'd just like to find out more about contemporary Catholic philosophy on this matter; I did some Googling but couldn't find anything relevant.

One random interesting thing: we have both German-language and Spanish-language services in our church; the words to the Spanish Gloria and Sanctus are always the same, but the words for the German Glorias and Sanctuses vary (if they're not the standardized ones, they are called Lied); but my priest considers this variation of the text practiced by German churches to be decadent / a corruption of the true text, and so we always do the same Gloria and Sanctus for the German-language services. So my interpretation is that, in this case, a change in the words is something that is being judged negatively by God, i.e. it is not good enough to worship Him. So I wonder if I can also do the same thing with musical notes, and so what should I avoid?...
Sacred music is "to arouse man's devotion towards God". God has no needs, being perfect in Himself.

Addressing "Whether God should be praised with song?," St. Thomas Aquinas answers:


  As stated above (a. 1),* the praise of the voice is necessary in order to arouse man's devotion towards God. Wherefore whatever is useful in conducing to this result is becomingly adopted in the divine praises. Now it is evident that the human soul is moved in various ways according to various melodies of sound, as the Philosopher states (Polit. viii, 5), and also Boethius (De Musica, prologue). Hence the use of music in the divine praises is a salutary institution, that the souls of the faint-hearted may be the more incited to devotion. Wherefore Augustine say (Confess. x, 33): "I am inclined to approve of the usage of singing in the church, that so by the delight of the ears the faint-hearted may rise to the feeling of devotion": and he says of himself (Confess. ix, 6): "I wept in Thy hymns and canticles, touched to the quick by the voices of Thy sweet-attuned Church."


*In that question, "Whether God should be praised with the lips?," he writes:Consequently we need to praise God with our lips, not indeed for His sake, but for our own sake; since by praising Him our devotion is aroused towards Him