If you're interested in checking out the song, there are various bootleg recordings available online, including the "Mayhem" version you mentioned, which seems to be a remixed or reworked version of the track.
You're referring to the infamous "Magic" outtake from Lady Gaga's album "Artpop"! Lady Gaga Magic -Mayhem Outtake- mp3
For those who might not know, "Magic" is an outtake from Lady Gaga's third studio album "Artpop" (2013). The song was produced by DJ White Shadow and Bloodshy, and it features a more experimental and darker sound compared to the rest of the album. If you're interested in checking out the song,