You dont need another call just to make that goosey noise. With your hands around the end of the call they should be quite restrictive but not enough that its to hard to blow through, any kindof sound should do but most say a form of "Guuu" or "Oooo" so if your doing a murmur call, its just a bunch of very low "Guuuu" the part that gets the sound even lower is when you put voice inflection into it, almost just like you're purring but "gurring" while you do it.
And then a simple honk it just stacked on top of that base sound "Guuu" and then adding "eet" at the top end, while opening up the end of the call. So its just "Guuu-eet" and you can make the low end short or quick for different honks.
Hope this helps, it could also be the tune on the call but then you'd have to change it around or get someone who knows how to do it help you.