1.
When you ~ 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 ~ 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