I have a stereo MPG file with left and right channels. How do I turn off vocals?

• Ordinary Karaoke songs have two stereo audio channels. One has vocal and the other one has music only. Our players only support this kind of Karaoke. There are some Karaoke songs that have vocal on the left channel and music on the right channel. Unfortunately, our players do not support this kind of Karaoke. Our players cannot turn off one channel for .dat files.