I wouldn't overthink it.
I use a whistle for field work. One that I get at Gun Dog Supply, not a silent whistle. Usually this one: SportDOG Roy Gonia Whistles and MEGA Whistles. because it doesn't blow my eardrums out and I don't need one for extremely long distances, personally. Different pips and tones for different cues. You might do a youtube search on whistle commands for field dogs or something like that to get some ideas.
I've never seen another dog go to a strange person using the whistle or even try to do so while at a hunt test or training. Dogs are contextual, so it's not like you'll be walking your dog off leash and someone uses a whistle and your dog takes off to a stranger. I mean, I guess it could happen, but it's not something I'd be concerned about.
I train all my dogs to the same tones.