Don't know which category this belongs in, but it's musical, and it says "according to one story," so maybe it's folklore. Switch it to a more appropriate category if necessary.

From "A Pictorial History of Radio" by Irving Settel:

According to one story, Miss de Leath was invited into the original De Forest Laboratory, where she faced a phonograph horn. Then, it is said, she sang "The Old Folks at home"--just for a lark. In any case, Vaughn de Leath, in the early 1920's, created the style of singing known as "crooning." Her style was imposed on her by the limitations of the radio equipment of the day, since the high notes of sopranos often blew out the delicate tubes of the transmitters. Ben Gross of the New York Daily News reported that "after her first broadcast, more than thirty years ago, Vaughn received one of the first radio fan letters ever written. It read: 'You have inaugurated a new form of song which, no doubt, will become very popular."

Sinatra, Bing Crosby, and those singers. I never knew there was a technological reason for their style of singing. The information's not folk music-related, but I thought someone might find it interesting.