If musicians who are preparing to play tune up their instruments, they make small changes to them so that they produce the correct notes.

After the orchestra had tuned up, the conductor walked on to the stage. 管弦乐队调试好音准之后，指挥走上了台。

He began to tune up his violin. 他开始调试他的小提琴。

to tune an engine

to prepare for something, or to prepare something for something, especially by making small changes to improve it

Microsoft is tuning up for the release of its latest operating system. 微软正在为公布新版本的操作系统而做好准备。

The group spent several weeks tuning up its act before the tour began. 团队花了几个星期为巡演作准备。