The aim of the study was to investigate the role of stimulus repetition during the on line processing of aural identification of harmonic sequences. This process involves (a) building a mental representation; (b) relating it to the knowledge base available in the long-term memory system; (c) selecting the correct label, and (d) writing the label without interrupting continuous listening. The time span between chords is decisive in this mechanism. Nine sequences containing eight harmonic functions of I, IV and V degrees were presented three times each. Subjects (N=/" undergraduate students) had to listen to each presentation and write down the label of each chord with Roman numerals while listening. findings show that the first presentation is a powerful image that influences the subsequent identification. Repetition favours the identification of those chords with had been omitted in the previous listening. Once the image has been shaped as a percept it will be difficult to change it. Then the response is incorrect, repetition was found to operate in a paradoxical way by imprinting the error. Many of the common practices in the context of the music class are based on repetition. Findings show that repetition per se does not provide a basis for the improvement of performance