Registration

Registration describes the different vibratory configurations available to the vocal folds, determined primarily by the balance between thyroarytenoid (TA) and cricothyroid (CT) muscle activation (Hirano et al., 1970). In modal or chest voice (M1), the TA muscle is more active, keeping the folds thicker and shorter with a longer closed phase during vibration. In falsetto or head voice (M2), the CT dominates, producing thinner, longer folds with often incomplete closure (Titze, 1994).

Titze (2014) proposed that register shifts can be understood as ‘bi-stable’ states of vocal fold adduction. Small changes in glottal convergence angle near the parallel position can produce large variations in driving pressure, causing sudden shifts between registers. This explains why transitions can feel unstable without proper coordination.

The interaction between registration and vocal tract acoustics adds further complexity. Large transglottal pressure differences can exacerbate bi-stability, while reduced pressure and balanced tissue stiffness facilitate mixed registration. Achieving consistent mixed voice across pitch, intensity, and vowel requires coordinating laryngeal muscle activation with vocal tract pressures (Titze, 2014).

Different pedagogical traditions use varying terminology: ‘chest’ and ‘head’ voice (experiential), M1 and M2 (mechanism-based), modal and falsetto (acoustic), or ‘heavy’ and ‘light’ mechanism (functional). While terminology differs, the underlying physiological phenomenon is consistent.