Epsilon-144
Musician and Producer
A drum bus combines all of the smaller parts of the drum beat into a single grouping. You can add effects to the entire drum beat using this drum bus (mixer track).
To do this, you'll want to add the parts of the drum beat one at at time to the mixer in separate mixer tracks. Add effects tho these individual tracks before routing them into the drum bus. Remove the Master (Mixer Bus) as the routing for each of these individual drum tracks. Instead, route these drum tracks into a new track called "drum bus". Now you can route this new drum bus grouping into the master (mixer bus).
Again, this lets you add effects and work on the drums as a group without effecting the rest of the mix.