You can control the Bose Hearphones World Volume and microphone Directivity with the buttons on the headset. But the free Bose Hear app offers a deeper level of customized control that really makes a difference. Bass and treble controls allow you to optimize real-world sound by making everything you hear brighter or deeper—your choice. With Music and call boost, you can emphasize the high frequencies to hear your Bluetooth® content more clearly. And with Ear balance, you can individually adjust each earbud to what sounds best—even turn one off.