Crosby, Stills & Nash are a folk rock supergroup made up of American singer-songwriters David Crosby and Stephen Stills, and English singer-songwriter Graham Nash. When joined by Canadian singer-songwriter Neil Young as a fourth member, they are called Crosby, Stills, Nash & Young (CSNY). They are noted for their intricate vocal harmonies, often tumultuous interpersonal relationships, political activism, and lasting influence on American music and culture.