To begin with, make sure that both of the 10S headsets are paired together so that they can talk over the intercom. Secondly, make sure that the headset that will be pairing the music is paired to a music device such as a smartphone.
Here is how to share music with another Sena 10S:
1. Start playing music on the 10S that will be sharing the music.
2. While the music is playing on the 10S, tap the Jog Dial once to connect to the second 10S headset. This will cause the music to be paused.
3. While both headsets are in intercom mode, hold down the Jog Dial for 1 second on the headset that is paired to the music device. You will hear a beep when you press down on the Jog Dial and you will hear 2 beeps after 1 second.
4. After 1 second and hearing the 2 beeps, let go of the Jog Dial and both headsets should now be playing the same music.