Frank Sinatra was an American singer and actor, prominent from the 1940s to the 1980s. Known for his warm baritone voice and phrasing, Sinatra was a key figure in the development of popular music and his style largely defined the big band and swing genres. His album "In the Wee Small Hours" (1955) is considered a major milestone in concept albums. Sinatra's impact on music history is significant, influencing countless artists and contributing to the canon of American song.