Companies and composers have begun using software to make music customized to your brainwaves. Soon you will be able to plug in your headphones, lean back in your chair, and relax to a playlist so synchronized with your brain’s chemistry that it increases your productivity, sleep quality, and even fights anxiety. The frequency at which your brain resonates defines your state of mind. Need to chill out? Try alpha activity. Or what about a pre-workout pep-up? Pop on some beta waves.