Pro Homepage is one of my favorite websites to remove vocals from song. Some of these sites also let you preview the output. Most of these sites support stereo tracks and use Out Of Phase Stereo technique to remove vocals from the added track. Still, it depends on how the input audio was recorded, audio quality, mixing of vocals, etc. It is handy when you want to make instrumental for a particular song or generate karaoke file.
Here are 4 free online vocal remover websites to remove vocals from song.
