1、《牽牛的夏天》主題曲是《偶然》。
2、歌詞:I am writing you a song don't want you to be alone,感覺的泡沫靜靜淹沒我,I wanna be your eyes stay with you all night,這眇小的我心裏只有一鼓衝動,Oh i have been loving you so long,想念偶然的笑容,怨家就像你和我誤會犯錯卻依然心動,Oh i have been loving you so long,偶然沒有能變有,想陷進你的生活;
2、不偶然愛過,i am writing you a song don't want you to be alone,曖昧的花朵,氛圍你和我,追逐你經過,替代你寂寞,這眇小的我,心裏只有一鼓,衝動,如果擁有如果,那麼,相遇在此刻,如果擁有如果,那麼,這生命會值得,Oh i have been loving you,想念偶然的笑容,請相信緣份繩索綁着你我一直到最後,Oh i have been loving you so long,偶然激起的花火,想成為你的生活,不偶然愛過,想成為你的温柔,不偶然愛過。