Scratching performed by a DJ (disk jockey) is a skillful style of playing the turntable with complex musical output. This study focuses on the description of some of the acoustical parameters and playing strategies of typical scratch improvisations, and how these parameters typically are used for expressive performance. Three professional DJs were instructed to express different emotions through improvisations, and both audio and gestural data were recorded. Feature extraction and analysis of the recordings are based on a combination of audio and gestural data, instrument characteristics, and playing techniques.

The acoustical and performance parameters extracted from the recordings give a first approximation on the functional ranges within which DJs normally play. Results from the analysis show that parameters which are important for other solo instrument performances, such as pitch, have less influence in scratching. Both differences and commonalities between the DJs' playing styles were found. Impact that the findings of this work may have on constructing models for scratch performances are discussed.

Kjetil Falkenberg Hansen got his PhD on analysing and modeling scratch DJ performances at KTH Royal Institute of Technology, Stockholm. He is currently associate professor of media technology at Södertörn University and senior researcher with the Sound and Music Computing group at KTH. At Sample Music Festival 2015, he gave an overview of DJ scratching techniques from various perspectives. The presentation covered several years of research on the playability of new musical instruments and a doctoral dissertation on the modelling of scratch performances.