In the 1940s bill monroe added two musicians to his band to complete the classic bluegrass lineup they were lester flatt and

Earl Scruggs

Bill Monroe and his Blue Grass Boys had their first appearance on the Grand Ole Opry stage in 1939. The band soon became one of the most popular bands because Bill’s band was different from other traditional country bands. It has a powerful sound that used traditional acoustic instruments. in addition to Bill’s powerful “high lonesome” solo lead singing.

In the 1940s Bill Monroe added Lester Flatt and Earl Scruggs to complete his line up.

imma say false because i dont know anything about this.