Whether it is possible to change the timbre during recorder playing is a much debated question among recorder players. Chen et al. (2007) showed that it is indeed possible to alter the timbre of the recorder as a player. As the underlying mechanism is not clear, a large eddy fluid simulation in two dimensions of four different vocal tract shapes has been carried out. One vocal tract is straight, the second one has a constriction in the back, the third one has a constriction in the front and the last one is a short reference model. The velocities and the pressure point to the hypothesis that turbulence created in the front of the mouth cavity is associated with lesser correlated velocities in the jet region and reduced harmonics.