Showing tempos and changes in tempo is a crucial part of conducting. Your singers must start at exactly the same tempo and remain together as the music speeds up or slows down. This is your responsibility. To speed up, reduce the size of your gestures since you have less time to make them. To slow down, increase the size of your gestures as you need to spread out the beats.

Here are three different situations involving tempo changes within a piece:

i) Changes of tempo between sections (involving a break in the sound)
ii) Abrupt changes of tempo
iii) Gradual changes of tempo