Rehearse your singing groups in small circles. It’s one of the quickest ways to get everyone on the same page.
Let’s face it: The biggest challenge in getting singers to blend, and be “one voice with many parts,” is that everyone tends to do their own thing. They do what in their minds is good singing, and it may be. But, it also may not fit in with what the others singers are doing.
I suggest having no more than 5-6 singers per circle for the best result. Having at least one strong, accurate voice in each circle is a good idea. You can start them in circles with their own parts, but that should be quickly moved to mixed-parts circles as soon are they are able. Instruct them to look at one another’s faces and mouths, even though this will cause nervous laughter at first.
What Can Be Accomplished:
Fine-tuning pitch. As singers are able to actually hear each other it’s amazing how they naturally tune up. Unifying diction. First, they will become diction-aware in a good way. Then, as they watch others working on pronouncing clear vowels and consonants they will fall into line.
Dynamics. Be sure to use exercises and songs that have varying dynamics so everyone can learn to move together. You should also have them lip-sync the words (no sound) during this exercise.
Proof of Success:
I use the circle technique in professional groups, church choirs and worship teams, high school and junior high groups. It always works!!!
I am betting that after even one extended session of working the circle you will have dramatically improved your singers’ sound. The proof will be when you let them back in their normal arrangement. You, and they will hear the difference, and this will likely become a regular discipline in your rehearsals. Let me know how it works for you at firstname.lastname@example.org.