The Underscore
The Underscore is a long-form dance improvisation structure developed by Nancy Stark Smith. It has been evolving since 1990 and is practiced all over the globe.
The Underscore is a vehicle for incorporating Contact Improvisation into a broader arena of improvisational dance practice; for developing greater ease dancing in spherical space—alone and with others; and for integrating kinesthetic and compositional concerns while improvising. It allows for a full spectrum of energetic and physical expressions, embodying a range of forms and changing states. Its practice is familiar yet unpredictable.
The practice—usually between 3 and 4 hours—progresses through a broad range of dynamic states, including long periods of very small, private, and quiet internal activity and other times of higher energy and interactive dancing.
           
There are 20+ phases of the score—each with a name and a graphic symbol—which create a general map for the dancers. Within that frame, dancers are free to create their own movements, dynamics, and relationships—with themselves, each other, the group, the music, and the environment. Each Underscore is unique, providing rich and often inspiring experiences of the human and artistic phenomena of dance improvisation.
The GLOBAL UNDERSCORE is an annual event in which the Underscore is practiced simultaneously for a 4 hour period by people all over world near the summer solstice (northern hemisphere). In 2012, there were 70+ sites. Claire Filmon proposed the event to Nancy in 2000 from a desire to connect dancers all around the planet to dance and to compose together in the moment and organized it until 2010. www.globalunderscore.blogspot.com
To participate in an Underscore, one should have some experience with Contact Improvisation and attend a talk-through of the Underscore, which often takes about an hour.
For more information, read the Underscore chapter in Nancy’s book: Caught Falling: The Confluence of Contact Improvisation, Nancy Stark Smith, and Other Moving Ideas, available through Contact Quarterly, www.contactquarterly.com. 
Here is the first page, about the history of the Underscoreand the second page, the beginning phases/glyphs of the Underscore, excerpted from Caught Falling.
To study the Underscore (and other material) with Nancy, go to her workshops/events page
– text taken from writings by Nancy Stark Smith, created in collaboration with various Underscore groups