To OP-
I recently travelled to Peru and did a few Ayahuasca ceremonies, but I didn't take very much. I stayed with two separate shamans/shamanesses, and in both situations the ceremonies were relaxed and often small (3-5 people), which was very nice. Everyone would drink and wait around in silence or quiet chatting until it kicked in, and then when it did, or at least for the shaman, he/she would start singing. The singing is very much the centerpiece of the ceremony. It's what drives the visions, it's what channels the energy and intentions of the ceremony. There is usually a shaker of some kind involved too.
Occasionally the shaman (if he/she's a good one) will stop and ask how you're doing. Everyone's got a bucket, and depending on the person, you use it or you don't. Ayahuasca ceremonies are HIGHLY variable. Sometimes no one will feel anything, and sometimes the night is so crazy you're not sure what's real and what's not. Ayahuasca is a very unpredictable beast in terms of strength of effects, quality of effects, and even timing of effects.
To jason7-
Very few people do Iboga ceremonies because
a) it's hella expensive
b) it's hella rare - I think it's actually endangered, or close to it
c) it's more physically dangerous than Ayahuasca
d) it lasts 3 days and ain't nobody got time for that unless you're a heroin junkie and you NEED to get off the horse
e) it's more intense than Ayahuasca. Yes, I said it. More intense.
f) legit Iboga shamans are very hard to come by, and most of them are probably in Gabon
g) Ayahuasca has been used throughout the Amazon, which is a pretty big place, whereas Iboga is traditionally used by one tribe (the Bwiti) in the tiny country of Gabon.
If I had to choose between Iboga and Ayahuasca, I would definitely choose Iboga, but that's just how my brain/body is wired. It just works better for me. I get more out of it.