The shadowy arm of the US Defense Department devoted to funding cutting-edge technology is building an interactive robotics system powerful enough to perform an incredibly difficult task: a trumpet solo. Defense Advanced Research Projects Agency (Darpa), the US military's technology research arm, has handed over its first cheque to Kelland Thomas, associate director of the University of Arizona School of Information (and a jazz musician in his own right) to fund musical machines. "The goal of our research is to build a computer system and then hook it up to robots that can play instruments, and can play with human musicians in ways that we recognize as improvisational and adaptive," said Thomas. Machine learning is a complex field, and one that a scientist at Darpa's Robotics Challenge in Pomona, California, earlier this year likened to "a three-day-old child". A three-day-old child's brain is incredibly powerful, but it doesn't yet know how to riff like Charlie Parker.