After searching for loops in the Loop Browser, you can listen to the results to find the loop that sounds best in your project. When you listen to a loop, you can hear it by itself (solo), or play it together with the project.
In the Logic Pro Loop Browser, select a loop in the search results list. You can either click on a loop to select it, or if a loop is already selected, use the Up Arrow and Down Arrow keys to select different loops.
The selected loop plays back in the project’s tempo and key.
Drag the Volume slider at the bottom of the Loop Browser to adjust the volume of the loop you’re listening to.
Click the loop again to stop playing.
Note: You can also trigger and stop playback of the selected loop using the Preview key command (default assignment: Option-Space bar). If you prefer, you can assign this function to another key command. See Assign key commands in Logic Pro.
By default, new projects have a key signature of C major. When you first add an Apple Loop to a new project, the key signature changes to the key of the loop. Each additional loop you add is transposed to the project key signature (or its relative key). Once the project key signature is determined, loops in the Loop Browser play in the project key. You can also choose to play loops in their original key or in a specific key in the Loop Browser and when you add them to your project.
In Logic Pro, click the Play in Key pop-up menu 
at the bottom of the Loop Browser, then do one of the following:
To play a loop in the project key: Choose Play in Project Key.
To play a loop in its original key: Choose Play in Original Key.
To play a loop in a specific key: Choose one of the available keys from the menu.
The Logic Remote app can mirror the filter settings you select in the Logic Pro Loop Browser. You can also use the Logic Remote app on your iPhone or iPad to change those filter settings in Logic Pro on your Mac.
In Logic Pro, choose Link Filter Settings to Logic Remote in the Play in Key pop-up menu of the Loop Browser.
When you link these settings across an iOS or iPadOS device and your Mac, changing the filter settings in the Logic Pro Loop Browser causes those same settings to change in Logic Remote, and vice versa.
To revert to Logic Remote showing all available loops regardless of the filter settings in Logic Pro, deselect Link Filter Settings to Logic Remote.
By default, Logic Pro automatically adjusts the volume level of Apple Loops so they play back at the optimum level when previewed in the Loop Browser or added to a project. This ensures that the loop volume is neither too quiet nor so loud that it clips the output. This adjustment is non-destructive, meaning the loop itself isn’t changed. For blue Apple Loops, the region gain parameter in the Region inspector is adjusted; for green, yellow, and violet Apple Loops, the track volume is adjusted.
If you prefer to not have the volume of loops automatically adjusted, you can turn off auto leveling:
In Logic Pro, deselect Auto Leveling in the Play in Key pop-up menu of the Loop Browser.
To turn auto-leveling back on, select the Auto Leveling again.
Note: Any loops already placed in the Tracks area are not affected by the auto leveling feature.