1. A system, comprising: a memory that stores computer executable components; and a processor that executes the following computer executable components stored within the memory; an input component that receives an audio signal excerpt and generates a spectrogram of the audio signal excerpt; an interest point detection component that generates a set of interest points for the audio signal excerpt based at least in part on the spectrogram, wherein interest points in the set of interest points are time-frequency points; a gradient component that generates respective gradients for interest points in the set of interest points based at least in part on the spectrogram, where each gradient comprises a ratio of a mean amount of energy in a window of the spectrogram prior to an interest point associated with the gradient as compared to a mean amount of energy in a window of the spectrogram after the interest point associated with the gradient, and each window comprises a plurality of time-frequency points; a descriptor component that generates a set of descriptors for the audio signal excerpt based on the set of interest points and the respective gradients for the interest points in the set of interest points.