Abstract  Recording of simultaneous but separated activity of neural populations overwhelms the experimenter with a large amount of information. A clearly structured display technique the Neurochrome is introduced, usable on-line and real-time. It shows neural activity patterns while preserving neural identity by employing a color code. The Neurochrome assists the experimenter in generating and verifying hypotheses about neural correlations and stimulus-event relations already during the experiment. In auditory research single neurons are characterized by their spectro-temporal sensitivity to auditory stimuli. A straightforward generalization of this concept, applicable to neural populations, is proposed leading to a global indication of a populations' activity to stimuli: the Multi-Unit Spectro-Temporal Sensitivity. This approach is inversely related to the Neurochrome, the latter however containing more information. The combination of both approaches seems quite powerful in the investigation of neural assemblies. The procedures are illustrated with examples of extracellular multiunit recordings from the auditory midbrain of the grassfrog (Rana temporaria L.).