About IVE (Sound)
They are basically a group who sings songs for adult computer games, but there are some non-adult versions of their games.There are conflicting reasons as to why it is "I've": see this Wikipedia article
Several I've members have branched out into solo careers, the most successful seeming to be KOTOKO.
In 2004, Anime Expo, a convention in America, hosted a talent competition to get a contract with Geneon Entertainment, formerly Pioneer, who is an I've "presenting" company, at least for KOTOKO and Mami Kawada. "The AX Idol winner in 2004, Stephanie Yanez, or STEPHANIE, was signed to record four songs for Geneon on the Anime Karaoke Collection CD."
Source: Anime Expo