As a musician and audio engineer, I'd be interested in an app that manipulated sound in various ways depending on mental state. The number of ways in which sound could be manipulated is vast ... some suggestions:
Using reverb, sound is further away or closer.
Stereo imaging: try to keep the sound focused in the center.
Amplitude: louder or softer
Equalization: low scores make sound midrange only (telephone audio), very high scores equal full frequency response (flat, no EQ curve)
Delay (echo): keep the sound repeating as long as possible (think of a soccer player kicking a ball into the air repeatedly, not letting it hit the ground)