That Sounds Like Ka Ka (Tremolo & Vibrato)

The tremolo, and in turn the vibrato (which uses the tremolo process as its engine) is performed from the vocal folds. A slight cough will give you the feel. Watch "Vocal Folds and Cough" to see what this is: http://www.youtube.com/watch?v=qpt0kigakWY It's common for students to unintentionally use a "Ka Ka Ka," thinking they're using their vocal folds, but they're not. No "Ka Ka" allowed... experiment and see what you're using. For more information on this technique visit the Tremolo & Vibrato lesson the site.