Yes, when moose are in the proper mood, they will come to almost any noise. I once very quietly eased my way a long a river flat, no moose. I wasn't calling, because it was only the first or second of September. Suddenly I realized I was supposed to be working very soon, so took off through the bush, paying no attention to being quiet. Heard the grunts, stopped, a moose came up to me, 35 yard shot.
The moose calling on some of the hunting shows on tv is pathetic. Still, a moose will come, in spite of the poor calling.
The string, heavy string like shoe lace and the tin can is great, for immitating the bull's grunt. Unless one hits the tin can a wrong way and a wary old bull will be gone, most likely without you even knowing he was there.
I have been very successful with just my mouth making the call. Your cupped hands help, but a birchbark horn I made and used for years, is far supperior to just cupped hands.
I learned to moose call by listening to the moose, not by immitating someone elses efforts, whether recorded, or not.
A good immitation of the cow call can be extremely effective. When I have been practicing, with no intention to shoot a moose, I sometimes have had trouble getting rid of the moose that would come to my call! A young bull doesn't want to take no for an answer.