All of the above are good suggestions and any of them might (or might not) work. One of the best methods I have found for achieving what you are looking for is to modify one of you current calls by changing the reed configuration/cuts or removing reed material.
I have made some of my best clear-sounding calls by doing nothing more than grasping the very outside edge of the top reed and popping off some of the material,...and continuing to do that with all of the reeds until I get the sound I am looking for. Pop off a tiny bit of reed material,...try the call,...and pop off some more. Eventually you should get the sound where you want it. I have calls that I end up with raggedy-edged reeds that have 1/3 of the original reed material left that sound fantastic and are really easy to run.
For those trying to get a really good clear and/or soft yelp and/or "tree call" sound, this method works great. It is also a really good use of calls that you have basically relegated to the "never gonna use these" pile. You will be surprised at how those calls will change when you modify the reeds or pop-off the reed material. Try it!
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