A whole view on the harmonic generation in organ pipes is presented. It consists ofelementary processes:(a) excitory source spectrum generation by the jet, (b) filtrationby the inharmonic normal modes of the passive system, and (c) radiation from the pipeends. Lateral jet velocity distribution is responsible for the source spectrum. Filtrationand radiation emphasize the resultant source spectrum. Harmonic generationmechanism is classified into the unsaturated and saturatea regimes, and formulated onthe basis of current-and pressure-drive models. Theoretical consideration deduced:(1) Contribution of the pressure-drive to the harmonic generation is not significant.(2) Harmonic structure and its development in the unsaturated regime are defined bythe matrix of the jet offset and the vector of the jet deflection amplitude.(3) A decisivefactor determining the harmonic structure in the fully saturated regime is the time interval ratio of the jet switching action.