"Those in charge of the music in the small church need to beware of the sin of carelessness. Those with richer resources need to beware lest they become concerned with a 'good show' and forget that the music of the Church is an offering to God, and that its primary purpose is to convey the Word of God and to contribute to the corporate worship of the congregation."
Those are two of the best criteria for judging both music and its performance in church: (1) conveying (I'd get picky and say "representing", but okay) the Word of God and (2) contributing to the corporate worship of the congregation. Especially (2) is an excellent wording - it doesn't mean that all music has to be congregational, but all music has to contribute to the corporate worship of the congregation. This includes a trained choir and the organ playing prelude music. That's appropriate, only insofar as it enhances the congregation's worship.