I have spent some time trying to discover the origin of the "Long Prayer" in the Reformed liturgy with little success. In the Reformed liturgy it takes place prior to the Scripture reading and the sermon. The prayer goes on for a very long time and is composed by the pastor. One time I happened to bring my child back from the potty and into the nave during this very long prayer and an elder came and scolded me later for offending God by walking in during this prayer. This prayer is clearly viewed as a high-point of the Reformed liturgy and given a special place. It could be argued that the sermon is the highest point in the Reformed liturgy but nobody gets scolded for walking in during the sermon.
In the historic Liturgy (followed by the Roman Catholics, Lutherans, Anglicans, and others) the closest thing I can find is the "Prayer of the Church" which takes place after the sermon. The pastor offers petitions using form prayers on behalf of the church (sometimes with particular names added) and after each petition the congregation responds with something like "Lord hear our prayer." Zwingli seems to have taken this prayer, removed the responses, and placed it near the beginning of the service. Bucer places the prayer after the sermon but removes the responses. Calvin does the same. They all use form prayers or create form prayers but they remove the responses.
It really puzzles me why those in the Reformed tradition would remove the congregational responses. One of their complaints about the Roman Catholic church was that they limited congregational involvement by having choirs sing the hymns. But the Reformed have removed the congregational parts in the liturgy and given them to the minister alone. In the historic liturgy near the beginning of the service the pastor says, "Our help is in the name of the Lord," and the congregation responds "who made heaven and earth" but in the Reformed liturgy the pastor says all of this. In some very conservative Reformed churches the congregation does not even say any part of the Lord's Prayer--the pastor does it all. The pastor is praying on behalf of the congregation and so theoretically at least the people are praying along with him even if not verbally but I really don't understand the reasoning behind this. If someone knows what the reasoning is I would really like to hear it. The current Reformed liturgy seems to follow the tradition of Zwingli by placing the prayer near the beginning of the service but I have been unable to determine when it switched from being a form prayer to a prayer composed by the pastor. My current theory is that this happened in America just because it seems like a very American thing to do.
The Reformed liturgy tends to partition prayer out as a separate thing from the rest of the liturgy. The historic liturgy tends to function as one long prayer but with lots of congregational responses throughout. I spoke with someone who was used to the Reformed style of worship and the prayers with congregational responses just didn't seem like prayer to them.
In the historic liturgy there are a couple of high points where special reverence is given. One of these high points is the reading of the Gospel. The congregation stands and sings Alleluia as the Gospel book is brought out. Christ speaks to us through the Gospel. The entire historic liturgy leads up to highest point which is the Eucharist. In the Eucharist Christ feeds us with His own body and blood. In the Reformed liturgy there may not even be a Gospel reading and there is no special attention given to it. If you were to ask most people what the most important part of the liturgy is they would probably tell you that the sermon is. The sermon is definitely important but if the sermon is simply the pastor providing some sort of verse by verse commentary then the liturgy becomes all about the pastor. In practice the highest point of the liturgy really seems to be the long prayer in which case the focus of the liturgy is once again on the pastor and the prayer that he offered that day. It would seem much more Christ-centered to return to the historic liturgy where we hear Christ speaking to us and He gives us His body and blood.