I read, you read. You studied, I've studied. We've done it and we haven't. Vocal warm ups. Hmm.
I know that warming up vocally is often compared to warming up the muscles. Well, you will find that some of the experts will argue that warming up can actually be detrimental to top performance. It can actually tire the muscles so that there isn't enough left to make a stellar performance. Now, just as there is an argument NOT to warm up there are arguments to the contrary. Be it ever thus.
1. Warm Up or Use Up - I agree that sometimes if people haven't sung for a while, they need to be careful not to come into a practice or performance and sing top notes at full force. I have vocal nodes from overuse of my voice as a music teacher and probably incorrect usage as a young person. I have only about 20 minutes of optimum singing and if I spend 10 of those warming up, then not much remains. However, I must not overdo the first part of my singing either. Common sense must prevail. If no warm up is used, start slowly and use mid-range music to start.
2. Specialty Warm Up - If we are doing a piece with larger intervals, or tricky rhythms etc. then yes I will do warm ups that focus on those new challenges. If we start to sing without a warm up and the sound is drooping or some are having trouble with staying in tune, then I will revert to some warm up material that places the tone correctly or focuses on breathing properly. I prefer to use a warm up for a specific purpose when needed.
3. Warm Up for Fun - That is self explanatory. Fun little songs sung as rounds or partner songs are great for upping the energy and getting voices in tune. Sometimes it is more important to warm up the mood or attitude than the vocal folds. You can start the practice with one of the choirs favourites and have then start with success and that sparkle that will carry them through the work of learning new challenging work.
The bottom line is that I think we should use discretion with warming up. Doing something all the time because you have always done it is no more helpful than never trying it at all. Make sure that your warm up routine is for purpose and that you all understand why you are doing each one. Don't spend a long time but have a good time doing what is best for all the singers in each situation.