Call the tune.
Call the tune.
To call the tune means to be in a position to dictate the actions or policies of others. It's comparable to a conductor leading an orchestra; just as the conductor decides the pace and progression of the music, the person calling the tune in any scenario decides what happens next. This idiom emphasizes leadership and authority, often used in business or group settings, where decisions by one person can dictate the outcomes for all involved. It underlines the power and responsibility of being in charge.
In this partnership, I call the tune.
In this partnership, I make all the decisions.
She's the boss, so she calls the tune.
She is in charge, so she makes all the decisions.
He likes to call the tune in every project he handles.
He likes to be in control and make decisions in every project he handles.