Two important aspects of singers’F0control have been investigated: vibrato extent and intonation. From ten commercially available compact disc recordings of F. Schubert’sAve Maria, 25 tones were selected for analysis. Fundamental frequency was determined by spectrograph analysis of a high overtone at each turning point of the vibrato undulations. It was found that the mean vibrato extent for individual tones ranged between±34and±123 centand that the mean across tones and singers amounted to±71 cent.Informal measurements on Verdi opera arias showed much higher figures. With regard to intonation substantial departures from equally tempered tuning were found for individual tones. A tone’s vibrato extent was found to have a negative correlation with tone duration and a positive correlation with intonation.