This.
I can purr somewhat realistically on a trumpet. It takes lots of practice and being consistent in the field is hard for me. Trumpets are best suited for clucks, yelps, cutts and even kee keeing if desired.
Dangerfield and Patrick Gamble are the two best I have heard in person with a trumpet- on every call that can be made with one.
I find that the purr is best made with tongue movement. If you practice long enough, it will click one day- but it's not easy to master.
I have been making trumpets and going to shows for over 20 years and I can count on one hand the people that can purr on a trumpet or wingbone.
Bob, not sure that is a contented purr at that. I've heard a few purr but it is more of an aggressive purr.
Whines are a lot easier to make on a trumpet, wingbone or yelper! Never seen the need for a purr on one, if he's that close, he should be dead!