I found this old, but interesting article:
http://www.dominionpaper.ca/arts/2003/09/12/new_brain_.html
If you don't want to read through the whole thing, I'll sum up the important parts: Scientists have found a way to increase musical creativity by isolating theta brainwaves. Unlike the method people here should be most familiar with, binaurals, they train people to increase their theta brainwave activity through focus, and providing feedback when the machine detects that this is achieved. Thus, you are simply trained to go into a specific state of mind, just that you have a machine to tell you what's the right state of mind.
Well, this article got me thinking. I would be in the market for such a machine, but even if the article stated where to get one, it probably wouldn't be that easy. But there are other ways to mess with brainwaves. For example, if someone made an .mp3 that uses a theta wave binaural beat while instilling a trigger to make the subject return to the same state of mind, only conscious, could that work? Or are there better solutions? Or is it something that probably wouldn't work at all through hypnosis?