Tuning Frequency Dependency in Music Classification

Abstract

Deep architectures have become ubiquitous in Music Information Retrieval (MIR) tasks, however, concurrent studies still lack a deep understanding of the input properties being evaluated by the networks. In this study, we show by the example of a Music Genre Classification system the potential dependency on the tuning frequency, an irrelevant and confounding variable. We generate adversarial samples through pitch-shifting the audio data and investigate the classification accuracy of the output depending on the pitch shift. We find the accuracy to be periodic with a period of one semitone, indicating that the system is utilizing tuning information. We show that proper data augmentation including pitch-shifts smaller than one semitone helps minimizing this problem and point out the need for carefully designed augmentation procedures in related MIR tasks.