the jazz that was popular during the 1930s and 1940s was known as 'big band' or 'swing' a big band or jazz orchestra,consisted of approximately 12 to25 musicians and contained saxophones,trumpets,trombones,and arhythrm section.the arranger called for an inprovised solo,a short piece of music created spontaneously by one of the players in many bands the arranger was also the bandleader