The idiom 濫竽充數 revolves around a story where a person, who is unable to play 竽 ( a kind of traditional musical instrument) but is able to join a 竽 musical team successfully. This idiom is used to mock someone who holds a position without having the required skills, or to describe a condition where an "unuseful person" joined a team just because "we need one more person to join, regardless of the skill".
This story will have many vocabularies related to music and performance, therefore suitable for intermediate learners.
In ancient times, the king of Qi country liked to listen to music, especially to the Yu. He now had 300 musicians who can play the Yu. The king likes to be lively, so every time he listens to the Yu, he always asks less than 300 people to listen to him together.
Someone called Nan Guo. heard that the king likes to listen to the ensemble, felt that he could take advantage of it, felt that he had a good opportunity to make money, went to the king and said: "The Great King, no one would not be moved by the Yu I played. The bird will sing when they listen to it, and the flowers will also dance when they listen to it. I want to tribute my (Yu playing) skill to the king." The king was happy and let him join the Yu group.
But in fact, Nan Guo cannot play Yu. Then what did he do?
At the time of performance, Nan Guo would bring a Yu and mixed himself with the team, imitating the movements of other musicians. Nan Guo did this day after day, and he got a very good salary without working hard for it.
But the good times didn't last long. After a few years, the king died and his son became a new king. The new king also loves to listen to Yu, but he likes to listen to a one-by-one performance. After listening to the orders of the new king, Nan Guo was very anxious. He thought about it back-and-forth and thought that there was really no way, except to pack his luggage and escape.