(57) An automatic music transcription system and apparatus for extracting the pitch information and the power information from an input acoustic signal, for correcting the pitch information in accordance with the amount of deviation of the axis of the musical interval of the acoustic signal in relation to the axis of the absolute musical interval, for dividing the acoustic signal into single-sound segments on the basis of the corrected pitch information while also dividing the acoustic signal into single-sound segments on the basis of the changes in the power information, for dividing the acoustic signal in greater detail on the basis of the segment information obtained on both of these segmentations, for identifying the musical intervals of the acoustic signal in each segment along the axis of the absolute musical interval, and further for dividing the acoustic signal again into single-sounds segments on the basis of the point whether or not the musical intervals of the identified segments in continuum are identical, for determining the key of the acoustic signal on the basis of the extracted pitch information, for correcting the prescribed musical intervals on the musical scale in the determined key on the basis of the pitch information, for determining the time and tempo for the acoustic signal on the basis of the segment information, and for finally compiling musical score data on the basis of the information on the determined musical scale, sound length, key, time and tempo.