Gradual change of tempo
The last type of tempo change is one where the tempo changes gradually over a period of time. It’s easier to slow down than speed up. A rallentando is basically a relaxing of energy, and singers have a natural tendency to slow down. On the other hand, an accelerando is more challenging since great energy is needed to prompt singers to get faster.

Rallentando
To show a rallentando, your beat pattern gets both slower and bigger. Your ‘bigger’ pattern travels a greater distance and therefore requires more time to do it.  The beat should be more angular as this will draw more attention to the slowing down. If the rallentando is to be dramatic, you may need to subdivide the beats.