Simplify the following text for a Grade 4 native English-speaking person.
Original: Rivers Cuomo ( Ë kwoÊ moÊ ; born June 13 , 1970 ) is an American musician , best known as the lead singer , lead guitarist , and principal songwriter of the alternative rock band Weezer .
Simplified: Rivers Cuomo ( born June 13 , 1970 ) is an American musician . He is best known for being a member of the rock band Weezer .