Headspace - Meditation made simple. Brilliant things happen in calm minds.
EarTrumpet - Volume Control for Windows
Medito - 100% Free Meditation App that will improve your Mental wellbeing with the help of Guided Meditations, Breathing Exercises, Mindfulness Practices, Relaxing Sounds, and more.
Sound Control - App-specific volume control
Calm - Calm.com can help you reduce stress and increase calm.
Power mixer - Power Mixer is a complete Windows volume control replacement.