You need to filter out the frequency range of human voice, typically around 600 - 2400 Hz.
Try to use a filter as narrow as possible.
Once you filtered out the singer's voice you can try to improve the sound quality by doing the following :
Try to mix an overlay of drums and percussion. In some cases you can use the extracts from the same track where human voice is not present.
You might need to remake some scores and mix them because filtering out human voice can filter some instruments out.
Use some audio editing software with VST hosting capability. On top of it, use a good mastering plugin to filter and equalize your track. I personally prefer iZotope Ozone and Waves bundle.
Good luck!
