Command group models cannot normally be removed as casualties unless there are no other rank-and-file members of their unit left. This applies even if the model is the target of an effect that affects only a single model, such as a dangerous terrain test, or an attack made with the Sniper special rule. Instead, normal rank and file models are removed first. They will either push the champion out of harm's way, step forward to raise the fallen standard aloft or will retrieve the instrument from the musician's corpse and continue to play.
When no rank-and-file models remain, the controlling player chooses the order in which the command group models are removed.