tune up | ˌtune sth ↔ ˈup
to adjust musical instruments so that they can play together :
The orchestra was tuning up as we entered the hall.
tune up | ˌtune sth ↔ ˈup
to adjust musical instruments so that they can play together :
The orchestra was tuning up as we entered the hall.
Oxford Advanced Learner's English Dictionary. Оксфордский английский словарь для изучающик язык на продвинутом уровне. 2005