Convert the audio to Mono WAV (16Bit, 44.1KHz). This can be done by using Cubase(Hope you got Cubase LE with Zoom). In an empty project import the audio, then mark the whole track using the Draw tool and then got to File->Export. Here select the above options and export. Import this file into Zoom H4 either by copying directly into the memory card or through connecting the Zoom to computer ( I copy it directly into the memory card's STEREO folder). Now if you import it to any project, it will appear there. You can now use Zoom H4 as a Karaoke device!! Anyway, sad that Zoom H4 doesn't support stereo tracks in the 4Track mode.