First download audacity is a free music editing program you will need to convert your music from stereo to mono.
Now run audacity and import the music you want to convert. Click on the file you want to convert in to mono.
Now look the box that appears for import your file. You should see blue waveforms. To the left of the waveforms, you will see a bunch of numbers and other settings in a box. In the top left corner of the box, locate the arrow.
Click to arrow and select Split Stereo Track from the drop-down menu. Now you will notice that track has been split into left and right channels that you can control.
Click the arrow by the top (Left channel) waveform. Select "mono" from the drop-down menu.
Click on the lower (Right channel) arrow. This will located to the left of the lower waveform's 1.0 marking. Select "mono" from the drop-down menu. At this point, the boxes to the left of the top and bottom waveforms should both say "mono.
Export your now mono song by clicking on the File tab and selecting one of the export options.
That’s it.