In The Great Gatsby, what does the phrase "banjos and traps" mean?

The question refers to a phrase in Chapter Three which is included in an overall description of the wild parties.

…and a great number of single girls dancing individualistically or relieving the orchestra for a moment of the burden of the banjo or the traps.

The banjo is a stringed instrument which was commonly used by Dixieland jazz groups. This suggests that the music most commonly heard at Gatsby’s parties was old-fashioned Dixieland jazz. The word “traps” means trap drums in this context. Trap drums are a full set of drums which always include a bass drum played by the drummer with a foot pedal, a snare drum, at least one brass cymbal, and miscellaneous percussion devices. The drummer sets the beat for all the other musicians, relying especially on the big bass drum.

Nick gives us a verbal picture of intoxicated girls who were trying to play the banjo or the traps while the musicians were taking a break. Nick specifies that they could only fool around “for a moment” before one of the musicians gently and respectfully took the banjo or drumsticks away. The girls wouldn’t know how to play the banjo or traps anyway, and they were too drunk to play them even if they did.

The Great Gatsby takes place during the Prohibition Era (1920-1933). Most of the people at Gatsby’s parties came there to drink illegal alcoholic beverages. F. Scott Fitzgerald focuses on the partygoers’ behavior. There is remarkably little direct mention of liquor because the publisher would not want to seem to be condoning violation of a federal law. Actually, however, liquor was plentiful—especially in a place like New York. Many people scoffed at the law, including many policemen. Fitzgerald could not show much of this in his novel, even though his hero Gatsby makes his money as a bootlegger; so Nick is given little to say about booze but much to say about its effects.