Can't Identify this Bird Call!

Hello, I'm new to bird identification, I just started a few weeks ago. I recorded a song between two birds that i just couldn't figure out what birds were making it. I have an app on my phone called Merlin Bird ID that I've been using to learn new bird calls.

But it seems I can't find this one anywhere.

I recorded it in a local park in Lincoln, NE.

Thank you to anyone that can help me identify them!