Simplify the following text for a Grade 9 native English-speaking person.
Original: The core of the group is the hard rock guitarist and video game composer Jun Senoue and vocalist Johnny Gioeli , who is also the vocalist for the bands Hardline and Axel Rudi Pell .
Simplified: The primary lineup from 1998 to 2009 consisted of guitarist Jun Senoue and vocalist Johnny Gioeli .