The best alternatives to Gaishan.io are Moises, Sight Reading Machine, and Riff Studio. If these 3 options don't work for you, we've listed a few more alternatives below.
Moises separates song tracks in various formats using machine learning for free. It leverages the power of a state-of-the-art source separation algorithm developed by Deezer. Upload a track (or use a youtube link) and get it processed in the cloud.
Riff Studio lets you build a setlist of the songs you want to practice, set their pitch and speed independently and before hand, so you can focus on playing your instrument or singing along!