The control modules
The design of the individual modules is finalized now. I've replaced the terminal block with a strip of headers due to the inconvenient fact that they were the most expensive part on the board for no reason. I added some space and tabs for board-edge mounting hardware.
I'm going to make a primary interface module that will have an expansion available for input from a 'keyboard' made up of arcade buttons or something similar.
I've found a source for small solenoid valves at $2 per valve, but they don't have enough throughput for me to be able to use them as basic input valves. I've experimented with rear-valving, but I'm getting the impression that I need to do something else, because they seem to have a tendency to squeak higher when cut off. I think I've got an idea for that, but it'll need testing. I'll post about valves soon.
I haven't done anything new with the horns yet. There are currently 1 1/2 inch, 1/2 inch, and 1 inch horns constructed. There will be 3/4 inch and 2 inch horns as well. No tuning has been attempted yet; this is likely to be the most time-consuming part of the project, and may yet prove uncomfortably inconsistent or difficult. There are lots of variables.