Buy every one you see!!!! research custom calls online. I have about 30 of them, learn them all and how they all sound slightly different. When you go out calling take what you think is you best mastered call and 3 or 4 more to very the verbalization. I've killing these predictors for 30 yrs now and being able to change things things up is the difference of a triple or a half dozen educated coyotes as they never forget a close call with a calling hunter.
I have called in probably 5-6 in the last 2 years (and I don't get to hunt yotes very much) with the orange primos ki-yi. It is a closed reed type, but is adjustable, so you can vary the sounds from a high pitch to a raspy jack.
a good open reed will also allow you to change sounds.