An apparatus and method are provided for processing an audio signal conveying a musical passage so as to reveal the sequence of musical chords contained within that passage. The signal is amplified, filtered, and converted to digital data, which are then processed using digital filters to determine in real time the amplitude of every note within a predetermined note range. The most prominent notes are compared to chord patterns to determine which, if any, chord is implied, and the chord name is then displayed to the user. Further provided is a means for detecting and correcting for any deviation of the pitches of the notes in the passage from their standard frequencies.