strike up
1．begin playing 开始演奏
People won't get up to dance until the band strikes up．音乐声起，人们开始跳舞。
The band struck up as soon as the Queen stepped on the shore．女王一登岸，乐队就开始奏乐。
2．begin a friendship with sb．建立起友谊
They struck up an acquaintance with each other on the beach and soon became very friendly．他们是在海滩上相互认识的，而且很快就建立起了友谊。
By degrees they struck up a friendship．他们逐渐建立了友谊。