In CALL mode, the sound is a MONO, 16kHz bit rate signal (most Bluetooth devices on the market use a lower 8kHz bit rate signal). When in MUSIC mode, the sound switches to STEREO with a 48kHz bit rate.
The higher bit rate of the STEREO signal means the sound quality in MUSIC mode is much better. Most Bluetooth devices do not allow you listen to music when you are talking or during a call using a mobile phone, computer, etc.
If you want to get better music sound in call mode, please click below FAQ.