ANEA,
From the description Shamanism sounds a lot like Magick and I was wondering if Magick isn't the core of all systems soever. I will start studying Shamanism once I finish reading Crowley's Libri as it must have very interesting methodological details.
I already met a South American group who appart from the other details also and especially used ritual drumming - Macumba. I hanged out with them for awhile and although their methodology isn't good I was able to learn great things. As how not to be affected by black magicians (trance of indifference under huge stress, at one point they wanted to rob my soul as I wouldn't participate on their rituals). Their work had a lot to do with the invocation of drunkyards and old people who had forgotten some message on their fridges, and so I left (my HGA must have wicked plans).
Thanks,
Love in Peace