Time-Frequency Reassignment for Music Analysis

Time-frequency reassignment may be viewed as a refinement of the short-time Fourier transform, in which phase information is used to reduce the smearing of energy associated with the standard spectrogram. However, even given the perceptibly clearer visual representation yielded by the reassignment method in the case of musical signals, the task remains of extracting useful information from it for further processing. To this end it is proposed that time reassignment information be used to help identify musical transients, and that frequency reassignment information be similarly employed as a means of estimating the pitch of musical signal components. To illustrate these ideas, an example is shown in which reassigned time and frequency points are used to segment a monophonic piano melody and locate the partials of its individual notes. Lastly, the potential role of reassignment in the overall framework of music transcription is described, and several areas are detailed for future study.