Open your preferred digital audio workstation, for example Audacity or Cubase.
Click the “File” menu, select “Open” and select “Recent.” From the drop-down menu, select the song session containing the stereo track to be edited.
Click on the stereo track in question, for example “Lead Guitar” or “Lead Vocals.” By clicking on it, you highlight it. This assigns each subsequent edit to that track specifically, rather than the mix as a whole.
Create a new channel. The method for doing this varies slightly between programs. Typically you do this by clicking “File,” “New” then “New Audio,” although some programs have shortcut tabs. For example, Logic has a "plus" icon for creating new channels. Name the new channel “Guitar 2” or “Vocal 2.”
Open the track settings information. The method for doing this varies according to which program you are using, but you typically click “Track,” “Track Info” or “Track Settings.” This opens a menu with multiple options. The options that aren’t available for this specific track are greyed-out.
Select the option that converts the stereo track to a pair of mono tracks. The methods vary according to which program you use. In Audacity, the free audio editing software program, you select “Split Stereo Track.” In Logic, click on the file, select “Edit,” then select “Disconnect Selected Split Stereo File.” Some audio workstations don’t automatically send the second mono file to a new channel; instead, they automatically delete it. In order to retrieve it, go to the “Audio Bin” section and drag the file into the blank channel. Now you have two separate mono files. You can edit each individually.