一般过去将来时有固定的结构：would/should+动词原形，也可以是was/were going to+动词原形。

所以sing的一般过去将来时就是：would/should sing或者是was/were going to sing。短语搭配sing the praises of高度赞扬sing a different tune改变（对某人或某物的）看法sing a different song改变（对某人或某物的）看法sing out the old year用歌声辞旧迎新sing in the new year用歌声辞旧迎新双语例句[in sing.]the lamps in the street shed a faint light into the room.街上的路灯将一缕微弱的光线投到房间里。[in sing.]he would walk up those steps with a confidence he didn't feel.他会带着不自觉的自信走上那些台阶。[in sing.]the ring road allows traffic to flow at a remarkably fast pace.环行路使车流能以相当快的速度行驶。Anyone who could play an instrument or sing in tune was roped in.会弹奏乐器或会唱歌的人都被说服参加进来。She began to gyrate to the music and sing a lewd song.她开始随着音乐旋转，并唱起一首下流的歌曲