We propose a simple model to describe the transient of our experimental recorder. The acoustic energy due to the formation of the jet, combined with an estimation of the steady-state oscillation amplitude and of the linear gain of the system, predicts a rise rime for the oscillation of the jet varying from 0.5 to 3 ms after the jet has reached the labium. It is only during this time that an edge-tone can coexist on the jet : there is no possible superposition while the jet oscillation is saturated. Once the jet oscillation is saturated, the model predicts a rise time for the oscillation in the pipe of the order of 0.1s. Our model shows a threshold (minimum driving pressure for oscillation) three times smaller than the experimental one. It also predicts the well known phenomena of higher mode transient typical for organ pipe.