Hi Philipzbinden,

we are sorry to inform you that these headphones do not support this option.
Each unit is suitable for specific side (right or left).
However, you can use the left unit alone while the right unit remains in the charging cradle.
If you use only the left unit, operate the connected unit to play music.
In this case, you can adjust the volume with the button on the left unit.
You can find more information about the functionality online on our support page.

Sony Europe

I don't think there is such a thing. Sorry for the disappointing answer.