A crooner is a singer that performs with a smooth, intimate style that originated in the 1920s. The style was made possible by better microphones which picked up quieter sounds and a wider range of frequencies, allowing the singer to access a more dynamic range. This suggestion of intimacy was supposedly wildly attractive to women, especially younger ones such as teenage girls, known at the time as "bobby soxers". The crooning style developed out of singers who performed with big bands, and reached its height in the 1940s to late 1960s.
Frank Sinatra in 1947
Gene Austin
Perry Como, October 1946
Bobby soxers were a subculture of young women in the mid-to-late 1940s. Their interests included popular music, in particular that of singer Frank Sinatra, and wearing loose-fitting clothing, notably bobby socks. Their manner of dress, which diverged sharply from earlier ideals of feminine beauty, were controversial. As a teenager, actress Shirley Temple played a stereotypical bobby soxer in the film The Bachelor and the Bobby-Soxer (1947).
Bobby-soxer jitterbugging with partner, circa 1945
American bobby soxer, circa January 1946
Crowd of bobby-soxers in Alameda, California; October 17, 1946