There are some huge drum sets that actually have two bass drums. I'm sure you've seen pictures of them. But usually, you just have the one bass drum, but it has two batters. So, your right foot is usually hitting the bass drum but then, your high hat foot, your left foot, also has a second pedal next to it with a sort of a long, you know, metal rod that reaches over to a second batter on the kick drum, so you can do double bass drum hits.