I have gone only so far as try out the free demo of holosync. They're using binaural tones for entrainment. This goes for Hemisync as well.
If you've done some further researches as I did in this field, you'll know that 'binaural tones' no longer holds the top position in entrainment. Research has found that
'Isochronic beats' is stronger and thus entrains the brain better than binaural beats. So, unless Holosync and Monroe Institute have upgraded their products to incorporate isochronic tones, then they're 'passe'.
Some respectable products that merged both binaural and isochronic beats are: the Neuroprogrammer and
Brain Evolution .
Do further searches and reading before you buy any product.
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Research Summaries/Articles: Brainwave Entrainment