The dirty rice call? That is a GREAT double reed duck call. I put mine back on the lanyard this past week after finding it in my big box of calls. It is quiet and ducky, even without the squeal.
You can do that squeal in two different ways, and it depends on how you blow a duck call. You can either intentionally 'over blow' the call, which will lock the reed up and produce the squeal. I find that method a little hard to control. The second way, which is in effect the same thing, is to slowly raise your tongue (the middle portion) to the roof of your mouth. This increases the velocity of the air flowing through your mouth and causes an 'over blow'. When I say slowly raise your tounge, I mean slower than you would normally raise it to shut off the air. So instead of a sudden raise of the tounge to shut off the air, like you would do on a normal quack, you raise it slower and let the call squeal. For me, this is much easier to control.
You can do this with just about any call by raising your tongue. I didn't bring the Dirty Rice back to my lanyard because it is easy to squeal, I brought it back because it is a good little call. A quiet little timber-type call with lots of duck. I try to keep a double reed on my lanyard or othewise close by just in case my single-reed calling isn't doing so well.
"I'll start spending less time with my dog and more with my wife when she starts fetching ducks for me"