Your body is your instrument. A good posture allows your breath to flow and give the voice room to sound. When we sing the voice resonates through our body.

Singing requires a certain amount of physical activity, though it should always be easy.. The body supports the voice. 

 

Your  solar plexus is the 'steering wheel'. Your belly is the storage of breath, your vocal cords a tool. By anticipating what you want to sing your body will respond and your mouth only needs to open to make your voice sound.