The Hammond organ is one of earliest electronic instruments and is still used widely in contemporary popular music. One of its main sonic features is the "key-click," a transient that occurs upon note onset, caused by the mechanical bouncing of the nine electric contacts actuated during each key press. A study of the dynamic mechanical behaviour of the contact bounces is presented, showing that the velocity, the type of touch and, more in general, the temporal evolution of the key position, all affect different characteristics of the contact bounces. A second study focuses on the listener's perception of the generated sound and finds that listeners can classify sounds produced on the Hammond organ according to the type of touch and velocity used. It is concluded that the Hammond organ is a touch-responsive instrument and that the gesture used to produce a note affects the generated sound across multiple dimensions. The control available at the fingertips of the musician is therefore such that it cannot be easily reduced to a single scalar velocity parameter, as is common practice in modern digital emulations of the instrument.