Bing Crosby and the Andrews Sisters were prominent American popular music artists whose collaborations in the 1930s and 1940s blended solo crooning with close-harmony vocal group singing. Crosby, a baritone singer and pioneering radio and film entertainer, was a central figure in popularizing a relaxed, conversational vocal style associated with traditional pop and early jazz-influenced balladry. The Andrews Sisters, a trio of sibling harmonizers, were known for their tight, swing-influenced close harmonies and upbeat renditions of popular songs, often incorporating elements of swing, boogie-woogie, and novelty numbers. Together they recorded a number of commercially successful and widely played songs during the World War II era, combining Crosby’s smooth solo voice with the trio’s rhythmic, harmony-driven backing.