The priority list for all of Sena's headsets (which is listed in the User's Guide) indicates which function will be interrupted by another function based on its level of priority. A lower function such as Bluetooth stereo music will be interrupted by a higher function such as a phone call.
(highest) Voice command mode (20S only)
Ambient mode (20S only)
Mobile phone (uses the HFP Bluetooth profile for both phone calls or GPS directions)
Stereo music by audio cable
Music sharing by Bluetooth stereo music (uses the A2DP and AVRCP Bluetooth profiles)
FM Radio (20S, SMH5-FM, SPH10H-FM only)
(lowest) Bluetooth stereo music (uses the A2DP and AVRCP profiles for music and GPS directions from a smartphone app)
The 20S is the only headset where it can combine functions using the Audio Multitasking feature such as Intercom + GPS directions (using GPS Pairing), Intercom + FM Radio, or Intercom + Bluetooth stereo music.