Instant City

Dan Hill at City of Sound points to Instant City (choose English, Projects, Instant City). From the project description (pdf), Instant City is a "music building game table":

One or more players at a table can create architecture using semi-transparent building blocks and in the process make different modular compositions audible.

Every performance is unique because the sequence, timing and combination possibilities are completely in the hands of the players!

More useful downloads, including a movie, are also available.