While karaoke programs can remove the vocals from a song, you may sometimes want to remove the beat, rather than the vocals. With the beats removed, you can practice drumming along to the song or use the vocals as an acapella track in a DJ set. The only way to perfectly remove the beats from a song is to alter the master multi-tracks for the recording; however, using a digital audio workstation like Audacity, GoldWave or Reaper, you can often remove much or all of the beat from a song.
Isolate the audio channel that doesn't contain the beats in your digital audio editing program, then duplicate this channel. Many older recordings have the drums on the right stereo channel and the vocals on the left channel, or vice versa. Removing the beats from this type of recording is easy: just copy the channel without the beats, then paste it over the channel that has the beats in it. This method preserves a great deal of the recording's original fidelity; however, you'll also lose any other instruments that are included on the drum channel.
Remove the beats from the song using the equalizer in your digital audio workstation. Cut out the frequencies around 60Hz; this will reduce the sound of the kick drum. Use a low-pass filter at a fairly high frequency, usually around 12kHz, to remove the hi-hats and cymbals from the recording. Removing the snare drum is tricky, as it occupies the same frequency range as many of the recording's other elements. Try lowering the EQ around 1kHz, and then again around 5kHz and 8kHz. Experiment with adjusting the gain and bandwidth on the various EQ bands until you get the best results for the particular recording you're working on.
Use a specialized audio plug-in to remove the beats. Voice Trap and Kn0ck0ut are freely-available Virtual Studio Technology plug-ins that can remove the beats from a song. ExtraBoy is a more powerful plug-in that lets you isolate and remove any part of a song; while it's not free, the developer offers a two-week trial version of the software. Open the song in your digital audio workstation, insert the plug-in on the same track, then adjust the EQ, phase cancellation and mixing sliders in the program until you no longer hear the beats.
Always respect a recording's copyright limitations when altering it.