I've always loved and admired how Steve can hold the Vibrato on the TONE ITSELF; NOT go sharp.....which is the ultimate in vocal control.
My apologies for not finding a better example...


Listen to the last sustained note:
American Express ~ Featuring Prelude from Bach´s Cello Suite No. 1
http://www.youtube.com/watch?v=m56F4EKN9hg
Compare it to his Vocal delivery, especially on the sustained notes:
Steve Perry ~ What Was
http://www.youtube.com/watch?v=j9iIYqFK ... L&index=32