croon / kroōn/ • v. [intr.] hum or sing in a soft, low voice, esp. in a sentimental manner: she was crooning to the child | [tr.] the female vocalist crooned smoky blues into the microphone. ∎  say in a soft, low voice: “Goodbye, you lovely darling,” she crooned. • n. [in sing.] a soft, low voice or tone: a gentle, highly expressive croon.

croon. To sing softly to a baby, but the wider usage since 1930s means to sing softly, and often sentimentally, with a dance band. Practitioners are known as ‘crooners’, the most eminent being Bing Crosby, though he was preceded by ‘Whispering’ Jack Smith and Rudy Vallee.

croon (dial.) bellow, roar, rumble XIV; utter a low murmuring sound XVIII. north. Eng. and Sc. croyne, crune — MLG., MDu. krōnen lament, mourn, groan (Du. kreunen groan, whimper), of imit. orig.