When you mix a project, you balance the different parts and blend them into a cohesive whole. You can also add effects to alter the sound, use routing and grouping to control the signal flow, and use automation to create dynamic changes in your project over time. You do this in the Mixer, which opens below the Tracks area or as a separate window.
Although there are no rules for mixing—except those learned from experience and a good ear—mixing typically involves the following steps. You may find yourself moving back and forth between steps as you work on the mix.
Set channel strip volume levels to balance different instruments.
Set channel strip pan, or balance, positions to place instruments in the stereo field.
Add and adjust effects and instruments to change the sound characteristics of a track or the overall project.
Control signal flow to create subgroups, route a signal to multiple destinations, or process sounds individually.
Create changes over time using automation curves on an individual track or the master track.
In the process of mixing, you can find different ways to accelerate and simplify your workflow, by muting and soloing channel strips, working with channel strip settings and Mixer groups, and customizing the Mixer.
If you are unhappy with any of your adjustments to channel strips or plug-ins in the Mixer, you can undo them using Mixer Undo.
You can also choose between different Mixer views when Show Advanced Tools is selected in the Advanced preferences pane, displaying only those channel strips that you actually need for the mixing task at hand.
Do one of the following:
Click the Mixer button 
in the control bar.
Choose View > Show Mixer (or press X).
Choose Window > Open Mixer (or press Command-2).
Do any of the following:
Click the Single button to show the signal flow of the channel strip that corresponds to the selected track in the Tracks area.
Click the Tracks button to show the signal flow of all channel strips that correspond to tracks used in the Tracks area.
Click the All button to show the signal flow of all channel strips available in the project.
Note: Aux and output channel strips are examples of channel strips that don’t have a corresponding track in the Tracks area. You can, however, create tracks for such channel strips by choosing Options > Create Tracks for Selected Channel Strips from the Mixer menu bar.
Use the Cycle Through Mixer Modes keyboard shortcut.
Click the disclosure triangle at the bottom of the channel strip in the Mixer.
Make sure that View > Follow Track Stacks is chosen from the Mixer menu bar to mirror the display of Track Stack subtracks in both the Mixer and Tracks area.
You can also perform some basic mixing tasks in the Tracks area.