Download Audacity, a freeware sound-editing software package that allows you to alter any sound files you import or record on your personal computer. Save the executable or .exe file somewhere easily locatable.
Install Audacity onto your computer by following the installation prompts that appear when you double-click on the .exe Audacity file.
Open Audacity, and import the song file you want to transform into a karaoke song into Audacity by choosing File > Import > Audio and locating the song file on your computer's hard drive.
Open each of the song's stereo tracks by clicking the arrow next to the track title in Audacity and choose "Split Stereo Track."
Select the right channel of the stereo track by clicking in the area near the mute button on the lower track.
Invert the track's sound by choosing Effect > Invert.
Change each track to Mono by clicking on the arrow next to the track title and selecting "Mono" for both the top and the bottom track.
Add each adjusted track to a CD burn list and burn your CD using CD burning software.