great organs in Cathedrals had a feature called “vox humana” or “human voice” which emulated the sound of a choir of thousands of voices singing. the range and versatility of musical expression of the organ surely make it most suitable to express the range of emotions and types of prayer expressed in worship, from despair, mourning, anguish and sorrow to joy, rejoicing, thankfulness, etc. My problem with organs in Catholic churches has always been that they seldom are played by someone with more than basic training, and seldom used to their full effect. It takes a good Protestant congretation to pay someone enough to make an advanced music degree worthwhile, and to really rock with the organ, let out the stops, and let the organ do what it does best: express the full range of human feeling that emerges in encounters with the Divine.