Different times, different religion. David wasn't "proclaiming the death of the Lord until He comes again". (I Corinthians 11:26) The Mass is a solemn sacrifice, and so the Psalms are chanted sweetly and piously.
Guitars and drums are not only inappropriate to the Holy Sacrifice of the Mass, they are an insult to it.
But the same God. And do you mean the OT is only for Jews?
I go to church to be uplifted and praise a God who loves me and not to honour any type of "tradition".
There simply is no such thing as "Christian" music. Music is tone, tempo, volume and melody. Instrument choices are irrelvant.