P300 components of event-related potentials (ERPs) were used to investigate the processing of different sounds in the human brain function. Defining the scalp topography of the P300 components by means of reference-independent method by using the Microstate Segmentation technique is the aim of this study. ERPs were recorded during a three-musical tones oddball task in eleven healthy, right-handed subjects. Microstate segmentation of the P300 responses yielded clear frontal region in both stimulus types. The deviant and target musical tones showed different scalp topography. Compared to the deviant musical tone, the target musical tone elicited a more prominent P300 occurring later than that of the deviant one. However, the deviant musical tone electrical filed had a more posterior distribution as compared to the target musical tone. Differences in scalp topography suggest that two stimulus types reflect different neural processes.