Wikipedia
Gnaural
Gnaural is brainwave entrainment software for Microsoft Windows, Mac OS X, and Linux licensed under the GNU General Public License. Gnaural is free software for creating binaural beats intended to be used as personal brainwave synchronization software, for scientific research, or by professionals. Gnaural allows for the creation of binaural beat tracks specifying different frequencies and exporting tracks into different audio formats. Gnaural runnings can also be linked over the internet, allowing synchronous sessions between many users.