Robert Godfrey points out that Presbyterian worship developed because of a particular theology, and that worship nourishes our growth in biblical understanding. If we adopt the worship pattern and emphases of another theological tradition, over time we undermine our biblical understanding of what it means for the people of God to gather before him to worship.
Some excerpts:
One area in which the differences between evangelical and Reformed can be examined is the matter of worship. At first glance, we may see more similarities than differences. The orders of worship in Reformed and evangelical churches can be almost identical. Certainly, both kinds of churches sing songs, read Scripture, pray, preach, and administer baptism and the Lord’s Supper. But do these similarities reflect only formal agreement, or do they represent a common understanding of the meaning and function of these liturgical acts in worship?
If we look closely, I believe that we will see the substantive differences between evangelicals and Reformed on worship. That difference is clear on two central issues: first, the understanding of the presence of God in the service; and second, the understanding of the ministerial office in worship.
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The Reformed faith has a fundamentally different understanding of the presence of God. God is indeed present to hear. He listens to the praise and prayers of his people. But he is also present to speak. God is not only present as an observer; he is an active participant. He speaks in the Word and in the sacraments. As Reformed Christians, we do not believe that he speaks directly and immediately to us in the church. God uses means to speak. But he speaks truly and really to us through the means that he has appointed for his church. In the ministry of the Word—as it is properly preached and ministered in salutation and benediction—it is truly God who speaks. As the Second Helvetic Confession rightly says, “The preaching of the Word of God is the Word of God.”
God is also actively present and speaking in the sacraments, according to the Reformed understanding. The sacraments are much more about him than about us. He speaks through them the reality of the presence of Jesus to bless his people as he confirms his gospel truth and promises through them.
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One great difficulty that we Reformed folk have in thinking about worship is that our worship in many places has unwittingly been accommodated to evangelical ways. If we are to appreciate our Reformed heritage in worship and, equally importantly, if we are to communicate its importance, character, and power to others, we must understand the distinctive character of our worship.Read the rest of Worship: Evangelical Or Reformed at The Aquila Report.
As stated there do not seem to be many differences until we see what God directs in scripture. Yes it is a fine line between them, but as we have seen in the past, drift away from God starts in small innocuous steps not huge leaps boldly stated leaps.