Hi - It sounds like you're talking about Audio tracks..? To set up different inputs on two Audio tracks in GarageBand to record two tracks at the same time, here's what you do: - Make sure the Track Header is configured to show the recording buttons: - Right-click on a Track Header or hit shortcut Option-T and check the Record Enable button - Select the first Track (Header), and open the Smart Controls pane at the bottom (shortcut B); - Make sure the Track button is selected in the settings panel at the left -- you'll see the settings for that first track; - Under Recording Settings, set the Input of that track (i.e. Input 3+4); - Select the second Track (Header) -- in the settings panel at the left now you'll see the settings for that second track; - Under Recording Settings, set the Input of that track (i.e. Input 1); - Enable the Record buttons on both tracks and begin recording.

If you haven't familiarized yourself with GarageBand's layout and terminology yet it would be hard to describe what to do in text. You can turn on the ? button (upper left) and when you point at different sections /controls in the GarageBand window it will identify and explain each section. A Track's Header is the gray area (where you see the name of the track) to the left of each Track lane (where you see the recorded MIDI or audio Regions). But the best course of action would be to watch a GarageBand course -- the videos will show what would be difficult to describe in text. I've attached a basic GarageBand course to this thread (More Info, above) -- the videos should show the general process of setting up and recording (it's the same course I attached to your other thread). If you go through the course, I expect it would answer a lot of basic questions, identify different sections and controls, provide visual demonstrations, and serve as a good introduction to working in GarageBand.

The link to the attached course is the More Info button above. That will take you to this page: https://www.macprovideo.com/course/garageband-101-absolute-beginners-guide?afid=E470KLQ7r9