DAFX: Digital Audio Effects, Second Edition

9.2 Sound-feature Extraction

9.2.1 General Comments

Sound features are parameters that describe the sound. They are used in a wide variety of applications such as coding, automatic transcription, automatic score following, and analysis-synthesis. As an example, the research field of music information retrieval has been rapidly and increasingly developing during the last ten years, offering various analysis systems and many sound features. A musical sound has some perceptive features that can be extracted from a time-frequency representation. As an example, pitch is a function of time that is very important for musicians, but richness of timbre, inharmonicity, balance between odd and even harmonics, and noise level are other examples of such time-varying parameters. These parameters are global in the sense that they are observations of the sound without any analytical separation of these components, which will be discussed in Chapter 10. They are related to perceptive cues and are based on hearing and psychoacoustics. These global parameters can be extracted from time-frequency or source-filter representations using classical tools of signal processing, where psychoacoustic fundamentals also have to be taken into account. The use of these parameters for digital audio effects is twofold: one can use them inside the effect algorithm itself, or one can use these features as control variables for other effects, which is the purpose of this chapter. Pitch tracking as a source of control ...