mp3 compression basically takes away all the stuff that the human ear "can't" hear, hence the much smaller file size. The holosync CAN be affected if you compress to a very low bitrate, this I have personally experienced. I believe holosync uses a sinewave to produce the binaural beat and then overlaps it with the soundtrack, which is why you don't hear the "whump whump" in your speakers you would normally get by taking a track and just "brainwaving" it. Binaural beats on a regular track, if the intensity is turned up, can become irritating, even inducing a tinitus feeling in the listener. Holosync is designed to be subtle, and as such I do believe a low bitrate (96 for instance) would be much less preferable a compression than 356, which is what I use for compression. The file size isn't much larger and the amount of quality retained is very worth the extra space. I think I just revealed my level of geekdom with that one, lol.