http://www.musicasacra.com/pdf/smfaq.pdf

Has some interesting points on sacred music as opposed to secular
eg. how that Elvis Presley hawaiin song may sound romantic but I personally feels that it does not elevate the sanctity of a church wedding (and that is totally the opinion of moi)

Plus it has some info on the use of organ as opposed to piano for liturgical use.

In general a good read.

Oz