The subglottal pressure (Ps) and voice source characteristics of five professional baritone singers were analyzed. Glottal adduction was estimated with amplitude quotient (AQ), defined as the ratio between peak-to-peak pulse amplitude and the negative peak of the differentiated flow glottogram, and with normalized amplitude quotient (NAQ), defined as AQ divided by fundamental period length. Previous studies show that NAQ and its variation with Ps represent an effective parameter in the analysis of voice source characteristics. Therefore, the present study aims at increasing our knowledge of these two parameters further by finding out how they vary with pitch and Ps in operatic baritone singers, singing at high and low pitch. Ten equally spaced Ps values were selected from three takes of the syllable [pae], repeated with a continuously decreasing vocal loudness and initiated at maximum vocal loudness. The vowel sounds following the selected Ps peaks were inverse filtered. Data on peak-to-peak pulse amplitude, maximum flow declination rate, AQ and NAQ will be presented.