Dic: call the tune, call the shots

7. PHRASE : V inflects | If you say that a person or organization is calling the tune, you mean that they are in a position of power or control in a particular situation.

• Who would then be calling the tune in Parliament?

...... Cobuild

CF. call the shots and call the tune: Fig. to make the decisions; to decide what is to be done.

• Sally always wants to call the shots, and Mary doesn't like to be bossed around. 
• They don't get along well. Sally always wants to call the tune.

CF. call (all) the shots: to decide on the course of action; to be in charge.

• Why do you have to call all the shots? 
• Do what you're told. I'll call the shots.

CF. call the shots/tune: to be the person who makes all the important decisions and who has the most power in a situation

.... McGraw-Hill Dictionary of American Idioms and Phrasal Verbs, 

Cambridge Idioms Dictionary,

http://idioms.thefreedictionary.com/Tune