If you want a near symmetric smile and clear diction, do the exercises prescribed below regularly. They were compiled from suggestions of professionals working in various aspects of a related industry, such as radio disc jockeys, speech therapists, & voice coaches. We can all improve in the area of intonation, voice, & mouth/lip control.
Here are some tips I’ve illustrated to best care for your vocal cords:
I also practice perfecting my voice pitch & tone by following the vocal exercises Roger Love created on a disc for his book called Love Your Voice.
Due to legal / copyright issues, I have included here instead a playlist to his YouTube videos that demonstrate similar exercises: