All music shown on PIXI.FM is delivered directly from YouTube through the use of their embedded video player. If you are a rights holder and don't want your video to appear on PIXI.FM, you have the following resolution options:
If you don't want your video on YouTube, use the YouTube DMCA takedown process to remove it. Videos removed from YouTube will also be removed from PIXI.FM
If you want to keep your video on YouTube but don't want it to appear on PIXI.FM, you can block it from being embedded through the YouTube interface. You are able to block all embeds or just the website https://PIXI.FM.
As YouTube is the source of what is shown on PIXI.FM, you must interact with YouTube directly to achieve your desired outcome. Any removals or blocks will immediately be reflected on PIXI.FM. If you have any more complicated needs please contact YouTube since they are far better versed in handling these matters.