Part two of a discussion…
This second thought has more to do with the craft of leading singing than theology, although if it is not done well it can distract from what the text is saying.
Leading a congregation in song is a lot like ballroom dancing (yes, I am stealing that from Richard Eyer's book, Marriage is Like Dancing, which is excellent). Someone must lead and the rest must follow. When there is not a clear leader in dancing, someone is probably going to get stepped on and may even fall down. When there is not a clear leader in congregational singing, the congregation will sing with less confidence and the tempo will often get slower and slower.
The thing is, someone will end up leading, even if it is unintentional. The kantor is the one best positioned to do so, and indeed that is his job. As I mentioned in the previous post, the term "kantor" (or "cantor") means "the leader of the congregation's song." The kantor's job is to lead and the congregation's is to follow. If he does not lead, whether it is because he does not realize he should be leading or he does not know how to lead the singing, the congregation has to pick up the slack.
Now, do notice that I said it is the kantor's job to lead the congregation's song, not the pastor. I am blessed to serve with a pastor who understands music and is a strong singer, but he also understands that the organ can lead the congregation more effectively that just one voice and that it is my job to lead the congregational singing. However, a well-intentioned pastor can undermine the kantor's leadership if that pastor does not follow what the musician is doing, but instead tries to set his own pace. If the hymns are consistenly too slow (or too fast), then he should talk to the kantor afterwards, rather than trying to change the tempo in the service. Now, there are certainly times when something goes wrong and the pastor needs to jump in to help the congregation get back on track. But if this seems to be a consistent problem, the pastor should go to the kantor and help him understand the problem and get the training necessary to enable the kantor to lead effectively.
So, kantors (church musicians, organists, whatever you are called), lead confidently, with a consistent, well-chosen tempo that fits the hymn you are playing. Your congregation will sing with more confidence and the music will be what it is intended to be: a vehicle for the text.