Thread:WakaFromStarAnis/@comment-28756829-20160712181207/@comment-25026534-20160712190338

With audacity ^^

It's free sound editing program, you can download it on official site

So you need to open the stereo audio file of the song, drop the track menu, choose 'split to mono', choose one of monos and go to Effects>Invert and than mix and render these two into single track ^^