The approach interactional prosody (cf.
couper-Kuhlen and Selting, 1996; also conversational phonology by Kelly and Local, 1989) suggests incorporating the following theoretical points toward the study of the sound system of conversational interaction:  The material considered derives entirely from naturally occurring face-to-face conversational interaction  The analysis attempts to prejudge as little as possible the salience of phonetic features  The analysis seeks explicitly to motivate and warrant the functional categories employed by reference to the observable behaviour of the conversational participants (Kelly and Local, 1989: 263) one of the features of the interactional prosody approach is that it advocates an 'impressionistic' analysis by closely listening to the production of real speech and notating phonetic details which a trained ear could perceive, including properties such as pitch, loudness, tempo, and others (Kelly and Local, 1989).