The letter "X" often functions like an open-ended signature, future-facing, representing an unknown quantity or quality. Taken on its own, it also resembles a figure with all limbs outstretched, reaching past one's foreseeable ends. It makes sense, then, that the letter flanks the name of Philadelphia-based contemporary ballet company BalletX, whose charge is to innovate, experiment with, and reformulate classical ballet for the 21st century. Founded in 2005 by Christine Cox and Matthew Neenan, BalletX presides over the 5,000-square foot Center for World Premiere Choreography, the organization's infrastructural incubator for new choreographic commissions by the likes of Trey McIntyre, Annabelle Lopez Ochoa, and Lil Buck. Whether staging pop-up performances across Philadelphia's historic sites and neighborhood parks or pushing the periphery of a traditional proscenium stage, BalletX's ensemble of tremendous movers injects fresh energy into the classical ballet idiom. In their Duke Performances debut, the company presents Neenan's playfully musical 2014 work Increasing alongside two additional repertory pieces.