Phonemic analysis must be based to a large extent on considerations of phonetic similarity and difference. For this purpose various stages of the speech event may be chosen, in particular the articulatory, the acoustic, and the auditory stage. It does not seem irrelevant which stage is chosen, for the analysis may give different results in each of the three stages. However, it is usually not possible to state general reasons for preferring one stage over another. In a given language functional reasons may in some cases decide the choice.