The natural purpose of any sensory system is acquisition of information on external processes and objects, i.e., abstraction of the stimulus. Abstraction, in turn, is typically dependent on decisions that are based on internal knowledge. To get more insight into auditory information acquisition—including perception of speech and music—it is thus apparent that particular attention should be paid to decision processes on any level of the auditory system. Inspecting the auditory system from that point of view reveals that both its physical and neurophysiological design and its psychophysical behavior indeed exhibit many cues that are typical of abstraction mechanisms. For instance, extraction of individual “pure tones” from a continuous sound spectrum requires a decision mechanism; therefore, the formation of spectral pitches in the auditory periphery may be regarded as a first step of abstraction. On the basis of a number of experimental data and theoretical arguments, the following questions will be discussed: (1) How is the hierarchy of abstraction organized? (2) Where is the “sensory knowledge” stored? (3) What is the origin of that knowledge? (4) Which strategies of experimental research appear to be appropriate?