Christian music is changing. It's changing both in form and style, in terms of how it's played and performed, but just as much, it's also changing people, leading them closer to Christ. Christian music has become more and more mainstream where it's hard to differentiate between mainstream music and Christian music. The difference between mainstream music and Christian music is that the Christian music lyrics are a positive alternative, not just another negative song out on the market.
Just the other day, listening to the radio, I heard Alive by P.O.D. on KROQ, an extremely secular radio station. This proves how Christian music is changing and evolving because it's becoming more and more adopted as normal music than it is this church-going, hymnal music.
Christian music is becoming more of a "positive alternative" than it is this independent genre of its own that people stay away from. The positive aspect of Christian music though, is the how the Christian lyrics are influenced. It's not the beat, it's not the sound, but it's the actual Christian lyrics that are being integrated into mainstream media.
Another band that can be captured in this is Switchfoot. Switchfoot lyrics are heavily influenced by Christianity, but they are not considered to be a Christian band by the secular world. They are certainly Christian rock lyrics, but still just rock lyrics in the eyes of the world.
There is the complete flip side of that though, such as Casting Crowns. Their lyrics are strongly influenced by Christianity and they are labeled as a Christian band because their music is more worship-focused. Christian worship music is almost a complete genre by itself because of how huge it is.
How has Christian worship music changed over time? It's become quite a bit more modern. Casting Crowns is a great example of how it's been modernized because it's not the traditional organ and piano, but you have the complete band with guitar, drums, including the piano. It's a complete band that sounds like a normal band, but it takes a worship aspect.
Christian music is a genre of music that cannot be ignored as a genre because of how massive it is. There are really no other religions which have such a prominent role in music as Christianity does.