Years ago, I used calls made from birch bark - available on trees between home and were I hunted. I found that similar results,with slightly less range, could be obtained just with the cupped hands & dispensed with makng a call "For that reason". With my hands, my 'call' was always with me. Moose calling tapes are fairly good, but generally have way too much bellowing in them and not enough talking.
: Moose talk to each other, just as elk and deer do, and 'talking', mewing, I called it earlier, in another thread concerning cow elk, is osmeting all the ungulates do, all the time. This sometimes gentle sound "errrunghhhh" or "orrrunghhhh" sound is easily made while walking through the bush and indeed, is exactly the sound ALL moose make while walking, bull, cow or calf, in different "tones" as they procede through their surroundings. Making this 'talking' sound, every 10 or 15', as you slowly walk throgh the bush, will allow you to walk right up to bull moose during the rutt, or to within 50 yards of closer to cows, but do be aware, sound too much like a bull, too much gruffness, or 'bark' and the bull you approach may be ready to fight as soon as you show up.