The MC has 1-Player and 2-Player modes. For example, one person can play one musical instrument, while the second person plays another instrument.
The MC can track many more people than this. The challenge, however, is that it becomes confusing who is doing what!
Having said this, there are ways to use it with groups, everyone dancing together. Methods for doing so will be explained in the on-line tutorial when MC3 goes on sale.