You can easily create karaoke tracks using Audacity. In case you are unaware, Audacity is a great sound editing and sound recording free source software that works on multiple platforms including Windows and Ubuntu. If you have never used it, download it, install it and try it out. It has great effects to boost your recording experience. Although you cannot create professional music with Audacity, for a free software it is a great tool.
You can create karaoke tracks with Audacity because it allows you to separate different tracks, manipulate them, move them around the timeline, create effects on them or all together remove them.
Karaoke, if you are familiar, is the complete song without the human voice. So with the same music you can sing like a professional singer. With Audacity you can create your own karaoke song by singing with the karaoke you have just created and recording the entire thing.
Unfortunately you cannot create karaoke out of an old song. You need songs that are created using multiple tracks. That is why you can manipulate individual tracks after opening the song in Audacity. Even on modern tracks there are good audio files and bad audio files. An MP3 file that is not compressed will create you a better karaoke compared to the one that is compressed.
You can access the tutorial on how to create karaoke tracks with Audacity on this link.