Mixed Reality Performance is an experiment in which physical spaces and Musicians from different continents encounter one another on-line. Promoted by MITO SettembreMusica in collaboration with the Stanford Humanities Lab and the Stanford Center for Computer Research in Music and Acoustics, this production is an experiment in on-line interaction among musicians in different locations. While a pianist plays their music is manipulated by other musicians on-line; from across the ocean other acoustic realities are manipulated and appear projected in 3-D on walls. Spectators are immersed in a recreated world of sound in an installation that marks the birth of the performance spaces on Sirikata, the most recent open source platform on the web.