This painting shows a Spanish gypsy dancer performing a flamenco dance to the accompaniment of several musicians and fellow dancers, seated alongside (visualartscork, n.d.). 

Sargent sought to translate the soulful dynamics of Flamenco onto the canvas. Although an ardent lover of Flamenco, Sargent also had the art world in mind when he painted El Jaleo ("El Jaleo Analysis", n.d.).

The main focus here is on the very moment where the dancer is turning. The meticulous details of this painting includes the angle of the half turn, the dancer’s posture and the play with shadows.

Sargent applied impressionism in this piece. 

The Impressionism technique is made full use of by Sargent as evident from the focus of shadows and light in the painting, especially the enlarged shadow behind the dancer.