1. WHY? Make certain your singers know what you want. You need to communicate to your singers where you need the differences in dynamics. Once they understand WHY they will be half way to making it happen. This means that you have to review your music carefully long before the first rehearsal.
2. WHERE? a) They all need to see where in the music you want the changes. For instance, this choir uses dynamic changes to enhance repeated phrases. The second time the phrase starts out softer and grows in loudness. Very smart. They obviously know that perfectly.
b) The second part of WHERE is the actual venue. This church has great acoustics. It really helps both the audience and the choir to hear those differences. Some venues may require just loud or fairly soft sounds. We have sung in small, tight venues and it is necessary to keep the sound more controlled. When singing in a huge space, loud might be required.
3. HOW? This conductor is using big movements and a great smile to connect with his singers. We don't get to see him all the way through, but when we do we can see why the choir members watch so intently. His motions are clear and helpful. Giving clear, concise directions is so important. Consistency is also essential. If you keep changing the spot where you want softer or louder sounds, the choir may get confused.
All in all, working at dynamic versatility, creates excitement in the singers because they are challenged. It creates excitement in the listeners because they are never quite sure what will come next. Keeping both audience and choir on their toes is just a lot more fun.