You mean the Soundtrap Karaoke Machine? We've got it! Use the Karaoke effect in the studio and listen to the magic! :D It works the best with high quality versions of the audio file so try your best to find one in high quality!
(1) Import an audio file with the song you want to use, open up the instrument view and add the Karaoke effect to the track.
(2) Use the Bass control to add back bass that was removed in the karaoke process.