Short documentary film which features the activities taking place in London's famous "Street of Song" (Denmark Street) - also known as "Tin Pan Alley." The idea of the film is to lift the veil and show cinema audiences just how a new number is created and set upon the road to success. The song in question is "Last Night's Kisses" by Sam Brown, Ray Hartley and Jimmy Kennedy. To help launch the song, stars come from far and near and are seen trying it out and discussing its possibilities.

Follows the development of the variety theatre from 1892 to the present day, centred on a family in show business.