Is your intention that you should hear the “music” and “music and singing” tracks playing at the same time? If so you will have to use Audacity. Drag both WAV’s into Audacity. The tracks will be one above the other.
If you are not sure if the tracks should be played together or not, just hit the big green Play button after you drag the WAV’s in and listen to what it sounds like. Press “Solo” if you want to hear what a track sounds like on its own.
If you still want to play the tracks together, just File > Export… . Audacity will give you a mono WAV with those two tracks playing together. If you want the same sound to come out of left and right speakers, that is all you need to do, assuming your CD burner can burn a mono file.
If the burner complains about a mono file, just do Tracks > Add New > Stereo Track before the export.
However you may want to play with the L…R sliders on the two tracks (look to left of the blue waves). Those sliders will let you make a stereo track out of the two mono tracks. For example you can make the “music only” track come more out of the left than the right. In this case you don’t need to add the stereo track at all. Just File > Export… .
Gale