You will have to revisit your basic knowledge of trading and the market participants because central banks and the commercial banks are major market participants in the currency and commodity market. The central banks are at the top because their involvement is mainly to sustain their exchange rates and maintain their national policy when it comes to money. For instance, Japan or China wants their currency a little weak, so their central bank will do everything including implementing excess supply to make this happen so they produce low and sell high abroad and make much profits. The point I'm making is that the central banks, the commercial banks, hedge funds and many other deep pockets are involved in the currency and commodity market... they provide the liquidity without which you will not be able to trade peacefully.