Clean Bandit  are a British electronic music band & songwriters who met when they were all at university together. The band consists of members Grace Chatto, and brothers Jack and Luke Patterson. Many of their projects are known for blending elements of both classical and dance music. They also often feature guest singers on the vocals. 

Stronger 

https://www.youtube.com/watch?v=_c_n0A3BFVE 

Symphony feat. Zara Larsson  - this is a live video so you can see all the instruments 

https://www.youtube.com/watch?v=pU_B-13jjkc&list=RDpU_B-13jjkc&start_radio=1&t=43 

Rather Be feat. Jess Glynne 

https://www.youtube.com/watch?v=2vzmZ57w158