1.
When you strike up a conversation or friendship with someone, you begin one. ( WRITTEN )
I trailed her into Penney’s and struck up a conversation...
PHRASAL VERB : V P n (not pron)
2.
When musicians strike up a piece of music, or when music strikes up , the music begins.
And then the orchestra struck up the National Anthem...
The band struck up, and riders paraded round the ring.
PHRASAL VERB : V P n (not pron) , V P