Load a digital copy of the song to be treated into your digital audio workstation (DAW) software. A free DAW called Audacity (see Resources) is available online. For the procedure to work, you must use a true stereo file. Sometimes older hits are mixed in mono, and not suitable for this use.
Apply the vocal remover plug-in to the audio track containing the stereo song file. Audacity has such a plug-in included. AnalogX has a freeware vocal remover DX plug-in, and Knockout Vocal Remover is a VST solution. DX and/or VST compatible plug-ins are accepted by virtually all DAWs.
Adjust the parameters of the plug-in you choose. Plug-ins may allow you to adjust the frequency range for vocal removal, leaving other center-panned instruments such as bass unaffected. Modify these settings until you get a result you are happy with.
Save your file to MP3, WMP or other format for playback. This may require you to export audio. Check the documentation of your DAW.