>I'd be interested to see if you could force yourself into getting beta wave activity in the brain by just listening to beta frequencies -- almost as if to tune yourself manually.

Does it actually carry over? From what I understand about the speech recognition, our brain must be doing some equivalent of the Fourier transform fairly early in the pipeline (i.e. instead of a beta-wave, our brain will just get a more or less constant signal that this part of the audible spectrum is currently active).