strike up
strike up  {v.}
1a. To start to sing or play. 
We were sitting around the camp fire. Someone struck up a song, and we all joined in.
The President took his place on the platform, and the band struck up the national anthem.
1b. To give a signal to start (a band) playing. 
When the team ran on the field, the band director struck up the band.
2. To bring about; begin; start. 
The policeman struck up a conversation with John while they were waiting for the bus.
It did not take Mary long to strike up acquaintances in her new school.
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Source: A Dictionary of American Idioms

