Even in my little mission parish here in South Carolina, we occassionally sing Tchaichovsky's setting of "Holy God". Its GREAT! I hear echos of monastic chant in it, esp. the base line. Granted it is in four part harmony, and well-polished musically, but it isn't theatrical or operatic at all if performed in a gentle voice. (I think one reason some people THINK much Russian Orthodox music is operatic or theatrical is because untrained voices (esp. tenors) tend to scream it when they sing, unless a firm choir director reigns them in. We have never sung any Rachmaninov, simply because I think its too difficult for our choir. However, Rachmaninov's setting of the Opening Psalm from Vespers (Bless the Lord, O my soul) still retains a haunting melody of the old Russian folk melody, although polished up and more elegant. I like them both.