Music is important in worship and in fact, it is one of the reasons I take into consideration as to why I go to the mass that I do. I realize that may sound conflicting because I started off by saying that it bothers me when people do that so let me explain. I enjoy the music at all of the masses at my parish because the music supplements the liturgy while not overwhelming and taking it over.
The particular mass I go to has a group of young adults leading the music. I wouldn't call it a "choir" nor would I call it a band. They have an acoustical guitar and a bass guitar as musical instruments but they are so subtle that in reality they could go without them and you wouldn't notice. They sing contemporary music while at the same time sing traditional Catholic hymns with a nice mix of Latin hymns such as Tantum Ergo. And by contemporary, I mean songs that might be sung by Matt Maher for Pope Francis and not any songs taken from the Glory and Praise hymnal.
I believe these young musicians at this mass do such a wonderful job in being reverent which in turn makes the music more prayerful and therefore more vertical. What I mean by being "more vertical" is that the music makes you focus upwards towards God in a form of worship as opposed to going vertical and being all about how great we are in the congregation. The music isn't about "I" or "we." The only time I've heard "me" being sung is when the request for God to "consume me" or "transform me."
The best way I can describe the music and the reason I believe that it fits in so well in the mass is because it is "prayerful." I get the sense that I am praying while singing. It does not feel like a perfomance is going on during the mass. There is no stage director cuing people in. There are no props.
And wouldn't you know it--the congregation is still "fully, actively, participating in the liturgy."