what?

• Lip trills are part of a family of exercises called “Semi-Occluded Vocal Tract” exercises or SOVTs.
  Semi-occluded means that the mouth is partially closed.
  The mouth being partially closed creates back pressure to the vocal folds. It’s essentially like swimming with water wings on – your voice gets help from the energy that is going back behind the folds as secondary resistance.

why?

Lip trills aim to:

• Create freedom in the lips and oral cavity, and facial muscles. If singers are engaging excess muscle action, as they ascend in pitch the lip trills will become difficult and cease to vibrate freely.
  Improve breath flow as the exercise requires the singer to maintain a steady flow of air in order to keep the lips vibrating.
  Lip trills can be done in head voice or chest voice. Play around with the strength and power of the lip trill to exercise a variety of tonal outcomes.

how?

• Lip trills are easiest when the lips are relaxed and a little pursed.
  Place your index fingers under the cheek bones on either side of your lips and gently elevate the cheeks so that your lips make a slight pout if you need a helpful trick to make lip trills easier.
  Keep the air flow steady and the lips loose. Try free-styling the trills in sliding patterns or follow the track and trill along to the simple melodic pattern.