concert       
noun [ C ] uk/ˈkɒn.sət/ us/ˈkɑːn.sɚt/
A2 音乐会
a performance of music by one or more musicians or singers
  a pop/classical concert 流行/古典音乐会 
 a school concert 学校音乐会 
 - More examples
 - I'm playing in a concert at the church hall next weekend.
 - All the mothers and fathers had been invited to the end-of-term concert.
 - The musicians are busy rehearsing for the concert.
 - The choir will be performing the Hallelujah Chorus at the concert.
 - She finished the concert with a song from her first album.
 
Idiom     
in concertidiom  (一同)演出
playing or singing with other musicians in a public performance
  She was appearing in concert at Carnegie Hall. 她参加了在卡耐基音乐厅的演出。 
  formal共同,一起;一致 
together
  If the member countries would act in concert, the problem might be solved more easily. 如果成员国行动一致,这个问题可能会更容易解决。