organ grinder:
(plural: ‘organ grinders‘; pronunciation: the letters ‘g’ in both the words are said with a ‘g’ sound as in “gun”)
a person/musician who plays a barrel organ on the streets entertaining people for some money, usually seen with a small monkey which collects coins from the passers-by,
Joe Bush is supposed to be the only known organ grinder still performing in the streets of New York, USA.
The adage “Speak to the organ grinder; not the money” means that you are advised to directly talk to the man in charge of something but not to the assistants, like the boss, because the organ grinder is the boss and the monkey is his assistant or attender who collects the coins.
There are occasions where we hear some politicians being called ‘organ grinders’ for their thoughtless actions or policies.

