1. Drag the music directly into the AU, and the editor will be opened by default. The upper and lower ripples represent the left and right channels respectively. If the sound on both sides is the same, you can look at the ripples and adjust the height.

2. If the contents of the left and right channels are the same, you can select one channel to delete, and then copy and paste the other channel in the deleted channel, so that the left and right channels are exactly the same.

3. If you want to delete it, click it near the edge with the mouse, and the other channel will be grayed out after it is selected. Press Delete directly for the selected channel.

It is suggested that you can go to the Internet to see relevant basic tutorials.