滥竽充数 ------ be there just to make up the member

例句：
A: Yon attended the singing contest last night.
你参加昨晚的歌唱比赛了。
B: I am there just to make np the member.
我只是滥竽充数罢了。

同义词：
pass oneself off as one of the players in an ensemble

注释：
singing contest 歌唱比赛