Does one person usually hold the ison for long chants? or do 2 people alternate? Is it always just one note? I'm still trying to understand it.
It isn't physically possible for one person to hold a sung or chanted note out that long, since circular breathing can't be used. The world record for longest held note by a vocalist is something like 1 minute, and even 30 seconds is exceptionally good. So it would either need to be two people, or else the person would need to stop to take breaths.
I agree also that you should definitely not get an ison machine! Do you think that chanters 100 years ago used a machine to do ison?
Well, not a modern machine certainly, since it wouldn't have been invented back then.
But, something like a didgeridoo
might have worked. Using circular breathing, a person playing a didgeridoo can hold out a single drone note for over 40 minutes. If the Apostles' first destination had been Australia, who knows what would have happened? The didgeridoo also has a very organic, more "human" sound, quite unlike anything in the West. It almost sounds like a chanter, just without words.
Interestingly enough, didgeridoo playing also has documented health benefits, including reducing snoring and sleep apnea.