There are multiple artists called XI:
1) Xi is the name of a doujin artist from the circle AQUAELIE that makes metal arranges of touhou music.
2) xi (Yusuke Ishiwata) is a Japanese music producer known for his BEMANI Simulation Files (BMS) and for his appearances in Rayark Games' rhythm series Cytus, which made him quite popular. He has been a member of the 100sec Records label until March 31st, 2014 and often appears in Diverse System compilations.
3) Xi start from the desire to play the best rock music they can to as many people as they can. Along the way they create songs that reflect their lives and relationships in an increasingly complex world.
Musically, they acknowledge their antecedents in rock while always striving to achieve something contemporary and new. Energetic, upbeat and complex enough to be interesting while remaining accessible enough to simply get down to. Sometimes anthemic, often challenging Xi present diversity within a solid rock foundation.
4) XI is a dubstep producer and DJ reppin' Toronto.
5) "XI" is one of many aliases of house producer Sven Rieger.