Simplify the following text for a Grade 9 native English-speaking person.
Original: Kim Thayil ( born September 4 , 1960 in Seattle , Washington ) is an American guitarist best known as the lead guitarist of the Seattle-based grunge band Soundgarden , which he cofounded with singer Chris Cornell and bassist Hiro Yamamoto in 1984 .
Simplified: Kim Thayil ( born September 4 , 1960 in Seattle , Washington ) best known as the lead guitarist in Soundgarden .