System and methods for characterizing interest points within a descriptor are disclosed herein. The systems include generating a set of interest points related to an audio sample. A set of gradients relating to respective interest points in the set of interest points can be generated. A set of descriptors can then be generated based upon the set of interest points and the set of gradients and used in comparison to reference descriptors to identify the audio sample. The disclosed systems and methods provide for an audio matching system robust to pitch-shift distortion by using gradients that characterize the time-frequency neighborhood around an interest point rather than solely relying on interest points themselves. Thus, the disclosed system and methods result in more accurate audio identification.