Io
It seems there are at least 16 different artists under the name IO.
1) Io was a emotive hardcore punk band from Pittsburgh, Pa, who released a full length and 7" on Hope Records/Hard Travelin and existed from 2001 to 2003 but played a reunion show in 2005.
Bandcamp
2) IO is a mostly instrumental, post-metal, math rock quartet from Birmingham, UK. Website.
3) Two talented music fans and DJ's are behind Ukrainian house music act 'iO': Alex Voznichenko and Artem Zhovtobriukh.