Whistles

I am currently in the process of putting whistles on my dogs. Craig came to me with whistles, so it seemed logical to just learn his whistles, rather than try to make up my own. When I get solid using whistles with Craig, I'll start Taz on them. I have a pretty consistent and somewhat strong come bye (Bob White), away (D-U-E), and stop whistle (drawn-out wheet with a little tail), but that's it. I find it more difficult to make a strong low tone, but my lower tones do sound a little more consistent. Craig's walk up is wheet wheet, but I cannot do this well at all, and he doesn't take it. As much as I try to practice it, I can only do one wheet at a time. It's hard to practice, as I can really only do so when I'm driving without the dogs, which doesn't happen all that often. Eventually the steady is going to be the drawn-out wheet without the tail, but I'm not worrying about that one just yet. Craig doesn't have a recall whistle, so I am trying to use a sort of high-low-high-low one. Unfortunately, he doesn't really take it, and neither of my other dogs come back to me when I use it when we're hiking on the trail. Well, actually Taz does recall, but he's happy to run back to me the instant he thinks I want him to at all, no matter what sounds I utter. Sophie, my third dog (who is a border collie mix and is not a good candidate for working stock--heh, wasn't that nicely put?), completely ignores this whistle, which is a shame. Before I got Craig and I was just playing around with my whistle, I mastered the D-U-E sound and used that as a recall whistle. Sophie would come running from wherever she was. Those of you who know Sophie will appreciate how amazing this is. But I stopped using this as a recall whistle because it is already Craig's away whistle. So my question of the day is whether these dogs can distinguish between working and hiking/playing contexts and I can use a recall whistle with Sophie when we're hiking that doubles as the whistle Craig (and eventually Taz) will take as an away whistle while they're working? My gut says that yes, I should be able to do this--after all, lots of people have a different set of whistles for each dog they have and their dogs don't seem to get confused. Of course, I don't want to make things more challenging than they have to be for Craig and Taz, but on the other hand, perhaps finding the one thing that Sophie consistently recalls to should not be tossed aside so hastily...