1. Download and install Audacity
2. Start Audacity and load your song of choice.
3. Open the track menu (click the arrow next to the track title), and choose “Split Stereo Track.”
4. Next, click the bottom track to highlight it.
6. Using the track menus, change each track to “Mono.”
Press the Play button to hear the results. If you are lucky, the voice will be gone but most of the other instruments will be unaffected, just like a karaoke track. You can then use the Export commands in the File menu to save the results.
Note : Audacity does not export MP3 files directly, but instead requires that you download a separate MP3 encoder. To know how to export MP3 files with Audacity, check this link
Thanks for Saquib and Abhishek for their inputs.