Simplify the following text for a Grade 8 native English-speaking person.
Original: In addition to his solo career , he was a founding member of three bands : The Byrds , Crosby , Stills & Nash ( who are sometimes augmented by Neil Young ) , and CPR .
Simplified: He is most famous as a member of the bands The Byrds and Crosby , Stills , and Nash , as having rather close relations with Neil Young .