One could say that the evolution of Interpretive Dance began with one woman, Isadora Duncan. As a choreographer and dancer, she shocked everyone with a unique dance, where she danced in a tunic, alone, in 1913. Scholars, dancers, thinkers, have ever since said she is mother of Modern Dance. Her "freestyle dance," as she called it, made an impact on the dance world, from composers, choreographers, to dancers, in the every mode of theatrical dancing. From Modern Dance, like many other dances, the highly unique art of Interpretive Dance arose. One could argue that Isadora Duncan was indeed doing Interpretive Dance in 1913, calling it "Freestyle." When asked about the Abstract or Freestyle Dance, she was highly theoretical in her explication, referring to Nietzsche and Ancient Greek god Dionysus.
As a branch of Modern Dance and the theatrics of dance, Interpretive Dance invokes the image of a single dancer or multiple dancers, all in black leotards, dancing unlike ballet or ballroom or anything one would assign as choreographed method. And like Isadora Duncan, Interpretive Dance needs theory, in a sense. Interpretative Dance is theatrical and expressive, conveying feeling, thought, intuition, and emotion, all through an improvised and/or inventive performance. When asked what her dancing meant, Russian ballerina Anna Pavlova replied: "If I could have said it, I shouldn't have danced it." In other words, Interpretive Ballet or Dance allows freedom to improvise, and, with techniques, such as a conditioning to rhythm, tempo, accents, steps--but more so, a mental and emotional conditioning--the dancer or dancers will effectively express something as simple as the aesthetics of the bodily movement to something as abstract or theoretical as political belief.
While the lone black leotard on an empty stage may be one type of interpretive dancer. Really, the concept can broaden into full theater, with costumes and set designs. It can be used in film and musicals, as well as ballet proper. Interpretive dance is to free verse as ballet is to epic poetry. And like free verse, audiences can either see the "freestyle" alone, or the context of all the elements improvised and composed. Interpretive dance is highly cerebral to interpret, but, when viewed, is free verse in motion.