The paper describes and evaluates the performance of several methods of larynx sychronous formant analysis for a female speaker. The techniques are based on the covariance method of LPC analysis and root solving of the coefficients to obtain the pole positions. The results obtained however, depend on both the length and position of the analysis interval. In this paper it is demonstrated that analysis over the closed phase of the larynx gives better performance than fixed frame length or analysis over the whole larynx cycle. The positions of the glottal closure have been determined using a larynogograph signal. The improved performance is demonstrated by a better ability to follow the transient features of the signal with fewer missed or extra formants, and better formant continuity. The ability to follow formant transitions during glides (e.g. w,r,l) and in voiced segments following plosives is particularly apparent. Closed phase analysis also shows improved performance over other analyses with white noise added to the signal.