PURPOSE: To make a singer to correct the interval by himself or herself by feeding voice information, which is corrected to the correct interval, back to the singer.

CONSTITUTION: An interval information detecting means 2 detects interval information from the voice information that the singer vocalizes and after an interval difference detecting means 3 detects a quantized interval difference from text data corresponding to a text consisting of a scale information sequence indicating the correct interval at each point of time of the interval information detected by the interval difference detecting means 3 and the music and determines a correction quantity, an interval information correcting means 4 corrects the interval of the voice information according to the determined quantity.