be there just to make up the number/pretend to be an expert
A man named Nanguo heard about that and he managed to become a member of the band, even though he was not good at playing the instrument at all.
Whenever the band played for the king, Nanguo just stood in the line and pretended to play. Nobody realized he was making no sound at all. As a result, he enjoyed his treatment just as the other musicians did.
When the king died, his son became the new ruler who also liked the music played on the yu. However, he preferred solos so that he ordered the musicians to play the yu one by one. Therefore, Nanguo had to run out of the palace.