1. When you play music, the message “Not available during a call” appears.
The Samsung bundled multimedia apps and the Google Music app are not designed to be used during a call. Download and use other apps from the Play Store.
2. Mono routing drops frequently while using the app.
Mono Mono is an app that changes the audio mode of your system to a virtual call state. Mono Mono will no longer work if another app changes the audio mode while using Mono Mono. There are apps installed on your system that change the audio mode, so please uninstall them or use only one of them.
3. The volume is too low.
By default, mono Bluetooth devices are tuned for call volume. For greater volume, turn up the system’s music volume before using mono mono.
4. Audio quality is poor
Mono Bluetooth devices have poor audio quality compared to stereo Bluetooth devices.
And in general, mono Bluetooth devices use less power than stereo devices, so you may not be able to play high quality music that requires more power.
It also sometimes depends on the situation of the phone you are using. For example, if the phone’s system is very busy, the audio quality may drop and then increase after the system returns to normal.