Background music: what can you make of the entertainment that gatsby has for his partys? Any signifigance?

The music would have been the boisterous Jazz of the 1920's. Fitzgerald coined the phrase, "the Jazz Age" that same year to describe the flamboyant orchestra-type Jazz,

"By seven o’clock the orchestra has arrived, no thin five-piece affair, but a whole pitful of oboes and trombones and saxophones and viols and cornets and piccolos, and low and high drums."

Certainly this paints Gatsby as a host with seemingly unlimited funds to throw a party. The whole time period also represented this decadent excess much like the music.