We just discovered that the terrific documentary, “Urban Symphony,” which follows the development of A Toronto Symphony, is available to watch on YouTube. This was the very first of Tod Machover’s City Symphony projects and we get to see how the composer and his team at the M.I.T. Media Lab collected sounds of the city and collaborated with school children, varied communities in Toronto, and the musicians of the Toronto Symphony to create this kaleidoscopic sonic portrait of the city.