maybe you know about the theory that it CAN be that brain cells can under certain circumstances be for a VERY short period heated to 10000° by electrosmog, in other words the electromagnetic signals from cellphones that go through you nearly all the time, at least if you live in a city.
well it's only a theory and the theory clearly states that it CAN be, but considering the amount of electrosmog that is produced today the probabilty rises quite high, so peoples brains or maybe only single cells or cell structures in it are fried.
about the brain machines.... it is true that the brain works when it completes multiple tasks at the same time or very fast tasks at a high frequency altogether, which define the state of mind. the same is true, about lower frequencies the other way round. also, by doing this an electromagnetic field is created, which can like any other electromagnetic field being induced by another frequency and "tune in" to it.
so depending on the frequency and the strength of a field or maybe a single vibration, the brainwaves can be altered. now the field of every person is different, simply because not every person thinks the same stuff and has not the same strength of emotion and thought, which can be seen as the electromagnetic field of the brain and body. i see thought and emotion as the primarily related factors for the experience of a being. at first there's the thought which brings the felt emotion and the emotion triggers new thoughts and so it goes forever on until death.
considering this brain machines might bring you the desired effect, but they also might bring the opposite. i saw some reports about this. in one of them a guy said he could induce religious experiences by such a machine. interestingly some persons that used this machine stated they felt a presence in the room which was pleasant for them and some stated they felt a presence, which was unpleasant. some said they felt relaxed and some said they felt fear and anxiety.