Listen to the Clarinet_1 and Clarinet_2 regions. They're the same musical material, and they're nearly identical, so it's too early to decide which one to use. But, let's label them so that we know they're the same.
Select the "Clarinet_1--L" region from the region list in the session toolbar by left-clicking on the triangle to the left of the blue name, so the white name appears, and left-clicking once on the white name. Remember that the white region was created when you trimmed the empty area out of the original (blue) region.
Then click again on the white name, and a text box will appear.
Change the textbox so it says "Clarinet_1A--L"
Press 'Enter' on the keyboard to set the name.
Rename the following regions as shown:
"Clarinet_1--R" becomes "Clarinet_1A--R"
"Clarinet_2--L" becomes "Clarinet_1B--L"
"Clarinet_2--R" becomes "Clarinet_1B--R"
Since Clarinet_1 and Clarinet_2 represent the same musical material, we've renamed them to show it. Now, they're both Clarinet_1, with two versions, "A" and "B."