Period-doubling occurrences in singing: the "bassu" case in traditional Sardinian "A Tenore" singing. Nathalie Henrich (1) , Bernard Lortat-Jacob (2) , Michèle Castellengo (3) , Lucie Bailly (1) , Xavier Pelorson (1) (1) Institut de la Communication Parlée (ICP) 46, Avenue Félix Viallet, F-38031 Grenoble Cedex 1 - France (2) Laboratoire d'Ethnomusicologie du Musée de l’Homme 17, pl du Trocadéro, 75016 Paris (3) Laboratoire d’Acoustique Musicale (CNRS - Université Paris 6 - Ministère de la Culture) 11, rue de Lourmel, 75015 Paris Introduction The human vocal-folds vibratory system is known to be a non-linear dynamical system (Herzel 1993; Titze et al. 1993). Evidences of bifurcation and chaotic behaviours have been found in the study of pathological voices, infant vocalizations, etc. In singing, period-doubling occurrences are commonly found in Asian vocal cultures, such as Mongolian Kargyraa throat singing or Tibetan Dzo-ke chants (Lindestad et al. 2001). A very low-pitch bass-type sound is produced by the combined vibrations of the vocal and ventricular folds (Fuks et al. 1998; Sakakibara et al. 2001; Sakakibara et al. 2004). In this study, we focus on a low-pitch singing technique found in a Mediterranean vocal culture, the Sardinian “A Tenore” singing. This traditional singing is still practiced nowadays in the central and mountainous part of Sardinia (Lortat-Jacob 1998). It is sung by a quartet of male singers, in an attempt to produce a single voice (Lortat-Jacob 1993). The lowest voice of the quartet, called "bassu", usually sings with a fundamental frequency of about 200 Hz but the perceived tone is half the fundamental frequency, i.e. around 100 Hz. We aim at describing the period-doubling phenomenon which occurs in this phonation, discussing its similarities with the Kargyraa throat singing, and briefly exploring phonetic and aeroacoustics correlates for period-doubling sound generation. Material and method To this end, a Sardinian quartet was recorded in an anechoic chamber. An electroglottograph was placed on the bassu's neck to get more information about glottal period and vocal folds’ contact area (Henrich et al. 2004). In addition, the audio and electroglottograhic (EGG) signals were also recorded for several vowels sung by a French singer trained for imitating the bassu's vocal technique. A videostroboscopic examination of both his normal and low-pitch phonations was performed. Results and discussion As illustrated in Figure 1 for the Sardinian bassu, and in Figure 2 for the French trained singer, the analysis of EGG signal and its derivative show typical period- doubling features. Vocal-folds contact area is modified from one glottal period to another for both singers. The EGG pulse shape is similar to what was observed by (Fuks et al. 1998) during “vocal-ventricular mode” phonation. The derivative EGG