"Dancers are instruments, like a piano the choreographer plays." - George Balanchine
When it comes to dancing and music, the two are so closely connected that each shares some traits with the other and each compliments the other to form a unique work of art and entertainment.
Dancers are musicians that "play" the instrument of their body. Every move they make is synchronized (or deliberately not synchronized) to the music, even if it's only music they hear in their spirit. Watching a dancer is like watching music come to life in picture form. While not all dancers perform to live music, they all perform to some kind of music. It may be the music of their soul expressing itself in movement, but it is music none-the-less.
So, in a sense, dancers depend on musicians for their art. Music enhances the experience for the dancer and the audience and lends depth to the story of the dance. The music lends mood and draws out emotions, therefore it sets the stage for the story of the dance.
Likewise,when musicians play, they also dance. Their fingers or hands dance across the instrument, creating a dance of body and notes that together fill the world with the beauty of music. They create a musical story for listeners to enjoy. One could envision each of the notes leaving the instrument and dancing through the air to land on the ears of the listeners, then dancing on into their mind and bringing them along for the dance.
When the two come together, the receiving audience is filled with the sound of the music at the same time as their eyes are filled with the movements of the dancer. Together they weave a story and a dance and this leads to an experience of even more senses and the listener/watcher's spirit feels and joins in with the facilitators of the sensations.
There are times, however, where there is no musician at all. The musician in some dance pieces is the human body. The can use their breath. They may incorporate sound by sliding their feet across the floor, or exhaling sharply and quickly. The instrument becomes an internal force in the dancer pushing its way out through the movement. Usually these dances seem to have more of a deep and personal feeling to the dancer, as it usually feels more internal.
An extension on the idea of the dancer also being the musician is the idea of body beats. A whole piece can be created off of the sounds that one can make with their own body. I like to think of this as a fusion of the dancer and the musician. The dancer does not find the musician within them like they do with breath as I stated above, they create the musician in their movement, playing the role of two artists at one time. An example of this is gumboot dancing. The entire piece is made up of different rhythms that are slapped and clapped off of the dancers' legs, arms, and gumboots. They add a sense of melody with vocal calls to specific movements creating an oral and physical harmony with themselves which is usually very pleasing both visually and orally for the audience.
I've never met a person who did not like music of some kind. They may not all like the same kind of music, but music resonates though every human being in one way or another. Thousands or more tune in to "Dancing with the Stars" on television and other dancing programs, eagerly awaiting the dance and music combo presented. They encourage those they like with their vote. They talk to their friends about the dances and music, often during the show through instant messaging or telephone. They remember which songs were played as much as the dances performed. They become addicted to the show which is, in essence, a marriage between dance and music.
True, the show is about the dance, but the dancers must have a "canvas" on which to create their art. The musicians are this canvas. They must keep a beat and create music for the dancers to dance to. If dancers cannot follow that beat, we know they didn't do well. Like a puzzle, when there is a piece missing, you get a feeling of being incomplete. When both are in sync, the viewer watches and listens with awe at the beauty created by this unique partnership: musician and dancer.