X-Minus.pro is described as 'This free online application will help you to remove or isolate vocals from a song using artificial intelligence'. There are six alternatives to X-Minus.pro, not only websites but also apps for a variety of platforms, including Mac, Windows, Linux and Python. The best alternative is Lalal.ai, which is free. Other great sites and apps similar to X-Minus.pro are Spleeter (Free, Open Source), VocalRemover.org (Free), Izotope RX 7 (Paid) and Splitter.ai (Free).
LALAL.AI introduces a new and improved way to extract vocals and instruments from music tracks. The new online service uses a machine-learning algorithm to precisely identify and carefully separate vocal and instrumental tracks.
Spleeter is a audio source separation library written in Python (uses Tensorflow). An easy to train source separation model providing already trained state of the art model for performing various flavor of separation.