The Key of C is traditionally associated with the Root Chakra. The Root Chakra is the seat of the essence of creation, your vital force, your purpose and the essence of who you are, your essential nature.
When the Root Chakra is open, you experience a feeling of calm self confidence, along with the energy of your creative vital force moving throughout the mind and body.
When the Root Center is blocked or bound by your emotions, memories and desires you often experience feelings of self doubt, a lack of purpose, along with the never ending list of questions concerning who am I and what is my purpose in life, leaving you feeling empty and not present, not grounded.
Learning to stay grounded and in the body is a very important first step in doing the work of bringing forward the essential self and experiencing the flow of your creative vital force. Opening the Root Chakra is the first step on this journey.
Here is a lively Flute Concerto in the key of C by Friedrich II (1712-1786), King of Prussia. He was one of the greatest commanders in history and a very interesting and complex character overall. For more music in the key of C, see this list of symphonies in C major and this list of Jazz compositions in the key of C.