The Trill: This can be practiced only when a singer is properly warmed up. The trill adds emotion to a song and is a more advanced means of expression. Many singing instructors suggest that this be practiced only when advanced control over the singing organs have been attained. While the trill can be as closely related to a type of 'scream' using your regular talking voice, it is used in song to accent message. Exercises that use trill should be done carefully, but require a confident student to use a lot of energy. Practice the trill on the same key and don't extend it past your own comfort level as you begin to use it. A proper trill can take at least three to four months to properly develop.
Velocity of the Voice: Trilling is associated with the ability to control the speed of breath that is emitted over the vocal organs. If you are not able to control the speed and power that are carried through your voice, then you have probably moved ahead too quickly. In order for your voice to gain velocity, you must first practice slowly. You will have to use your nasal singing skills, and be able to resonate sound properly through your head voice in order to add this 'velocity' to your voice.
Trill and velocity are all factors that will give your voice a new vocal range. Again, these advanced methods of singing are not for those who have just begun, but are for those who have at least mastered their own breath and who understand the importance of practicing to sing. Self-monitoring, or monitoring your singing progression by a singing instructor is one of the best ways you can fully use each practice session to your advantage.