Behringer Mixer

People can use their home computers to pursue karaoke as a hobby and there is no need for expensive professional equipment. An average desktop computer sound system is fine, especially if it has a sub-woofer. Laptop users can connect the headphone sound output into an auxiliary input on a home hi-fi system. Getting a little more professional you could insert a Behringer MIX800 Minimix Ultra Compact Karaoke Machine between the computer and sound system which would enable the use of a microphone with echo.

Your local karaoke dj may use cd+g disks in a special cd player, however these cd+g disks can be turned into mp3+g computer files. The conversion is similar to ripping a cd into mp3 files. There are several software applications that will rip tracks from a cd+g disk and convert them to mp3+g files. A popular free one is AudioGrabber which needs a lame encoder dll placing in the programs folder to enable high quality mp3 rips. The guide for Audacity outlines the method to install lame in Audiograbber. Before you can rip tracks from a cd+g you must have an optical drive (dvd-rom, dvd rewriter ect.) that can read subchannel data. To maintain cd quality sound the encoding of a mp3+g track should be at a minimum of 192kbs. The resulting small mp3+g consists of two files, an audio track in mp3 format and a separate graphics file that has the lyrics. This is a good Audiograbber guide.
Songs can also be downloaded in mp3+g format from a variety of websites. Sunfly is a leading manufacturer of karaoke disks and they also sell mp3+g downloads. Beware of the bittorent sites as this is a certain method of infecting your computer with viruses.

Once you have your mp3+g karaoke files they can be played by many software programs. Winamp is an excellent free program which when combined with this free Plugin will play your songs.

Audiograbber and Winamp screenshot.
The above screenshot shows Audiograbber on the left and Winamp on the right.

Finally burning mp3+g files to make a cd disk requires special software. I recommend the inexpensive Power CD+G Burner.