So what exactly makes christian music christian? The lyrics? The atmosphere? The melody? The conviction of the performers?
Funny how most people actually mean 'MODERN christian music' when they talk about 'christian music,' though 'worship music' (etc) is a relative newcomer. Christian music has been around for over 1500 years, from the earliest hymns to the present day. The lyrics have always been important, but sometimes the melodies of these songs became so well known that they could evoke the some 'religious sensation' in their own right. Just think of the the stringquartet on the Titanic that played 'Nearer my God to Thee' as the ship went down; the people aboard got the message alright, even without the lyrics to that song.
It's interesting to see how many of the christian hymns were inspired by secular songs, take for instance the melodies of the 'Geneva Psalter.' And J.S. Bach had no problem reusing the music of his secular cantatas for solemn occasions, he was a very practical man.
Whether music is 'christian' judging by its 'atmosphere' is an interesting point of discussion. We can have our doubts about 'christian metal' being christian, for instance, I mean: it's loud, 'heavy' and very serious in tone. I myself wonder why there is so little REALLY good christian dance and trance music available; the overall atmosphere of such music fits the act of worship much more that metal does: it's optimistic in tone, uplifting, extatic.
Modern christian music usually is mediocre compared to its secular counterpart. A lot of mediocre christian bands make a good living with their music, not necessarily because of the quality of their music, but because the christian lyrics and the coniviction of the band members gets them a loyal crowd of fans. I mean: if you expect the band to be christian, and the lyrics ONLY to be inspired by the Bible, you have to be content with such bands.