I’ve been invited to a summer party by one of my online friends(who I’ve never met in the flesh - in fact I’ve never met any of the folks at the community in question; they are all arty types)
Anyway I won’t be able to attend, but I’m intrigued by this bit in the invite:
I’ve heard some of them talk about ‘drumming’ before and whilst I fuly understand what a drum is, I can’t quite see the appeal of doing it en masse.
Somebody enlighten me, please?
Its pretty much just a bunch of damn hippies sitting around in a big circle, each with a drum that looks like a large bongo, and they wail away in unison while they smoke up and drop acid.
Are you a damn hippie? 
You don’t need pot or acid. Group drumming is hypnotic all by itself.
No, I’m not a hippie, but that would perhaps be a fair description of some of the people expected to attend. I suspect that some form of recreational drug use will be involved in this case though, hmmm.
Drum circles have been around for ages and only recently have become a “hip” thing to attend.
Basically, there’s a facilitator who sets up some rhythms and has everyone else join in on all sorts of percussion instruments.
There may not be a facilitator at your group. In that case, there’s usually a few experienced drummers in the group that set up a beat and get everyone else to join in.
I’m a drummer of 30+ years. I play a drum kit like you’d see in most bands. I also play all sorts of hand-drums and have been involved in literally dozens of drum circles.
To me, it’s a relaxing and nearly-hypnotic way to spend an evening. Afterward, I feel refreshed and invigorated. The feel of the beat pulsing through my body is much like getting a massage.
But it’s not for everyone. You might want to wear hearing protection (small foam cylinders work well. they’re inexpensive and can be found at Home Depot) because it can get a bit loud. Some like to dance (think Grateful Dead) and some like to chant. Someone may bring a who sackful of percussion instruments (tambourines, shakers, maracas, lummi sticks, etc) or extra drums. Don’t feel shy about asking someone if you can play their instrument. Most people are pretty proud of their drums!