The distinction between liturgical music and that composed merely for entertainment has been mentioned. But, even that distinction can get blurred.
In the Orthodox shul I attended back in the 70s, there was a brief period when the some of the younger adults would “creatively” incorporate into the kedusha of Shabbos musaf popular melodies heard on the radio and in theater (I don’t think they ever consulted the Rabbi beforehand).
But if you consider the fact that music does tend to bleed through cultures, at what point do you say “this has x% influence from pop tunes and is therefore bad?” I’m not advocating setting kedushah to a Michael Jackson tune, but where is that line?
Probably the most bizarre of the lot I can recall was a visitor who used the title track from the Broadway musical: ‘JC Superstar’.
Admittedly, that one is a bit bizarre. But as long as we’re on the topic of Andrew Lloyd Weber, I have to state that the tune of “Any Dream Will Do” from Joseph goes very well with some Shabbos Z’miros. 🙂
The Wolf