(1) Tt is an artist based in Brisbane, Australia, also known as Titee.
http://www.last.fm/music/Titee
http://titee.bandcamp.com

(2) tt is a German artist.

(3) TT is also a portuguese rap/r&b singer and composer

(4) TT is the pseudonym of Warpaint's Theresa Wayman. Her debut album 'LoveLaws' is due for release on the 18th May 2018 via Caroline.