It's time of year dependent, Will. Early september bulls respond to vocal and auditory responses from bulls and cows. First 10 days of September (global cycles vary this date), bulls rub velvet off antlers as they harden...so smacking trees, thrashing willows and spruce, breaking wrist-size dry wood, but very limited vocal commo.
After the 10th bulls will begin responding more readily to vocal calls.
Moose differ from elk in one major way, which is in response time. A smart (or pressured) bull will not easily be coaxed in to a call location. I've observed moose cover 2 miles in less than an hour to address some curiosity or purpose, and I've witnessed more often cautious bulls refusing to move for many hours before creeping into view of our camp to locate the source of the calls.
If you're looking for a blind calling method that is a no BS, simplistic method that works 95% of the time?
Establish a camp within freshly used corridors and conceal your noise and appearance. Break wrist-size debris or chop deadfall with a hatchet every 20-30 minutes for a minute or two in length. Do this during cooler hours of the day to match the expectations of real animals in that environment. If it's 70+ degrees, bulls are likely bedded in the shade and certainly not actively calling or investigating.
This is why you often hear of hunters calling all day and evening, and then having a bull show up that night or the next morning. These bulls have to conserve energy and carefully manage body temperature...hence why the first and last 2 hours of the day are generally more productive.
