The final version of Invitation to the Sideshow was one of a number of works featured at the Salon des Independants in March of 1888.
The human figures of many of Seurat's works, are generally characterized by an aureoles, or "aura," whereby a lightening of color surrounds the figure in places, giving it a certain definition against its surroundings. We see this method used early in Bathers at Asnieres, and it makes a particular impression with Sideshow, given the brilliance of the gaslighting against the night.
Through the use of this technique, the luminosity clouds the musicians in the background to the left, as it diffuses the color that defines them. By contrast, the light gives definition to the bandmaster, making ready to announce the next act. At the center is the trombone player, dressed as a clown, his darkened figure backlit by the gaslamps. Below, in the darkness, are the onlookers, lining up to pay their tickets to the performance.
Duchting calls this "Seurat's most mysterious and darkest painting." (page 56) One might beg to differ; there is a sense of merriment throughout the scene, as the people are drawn to the music and the light.