Similar to the discussion about stereo pairs and volume control, I feel group or individual volume control should be configurable options. While you may wish your three group members to be assimilated into one entity with a single group volume control, I might equally have such a group (say “downstairs”) with three devices, all the same or different, some with their own speakers or feeding different audio systems, where I’d want the kitchen, lounge and dining room devices to be able to control the volume commensurate with their environment , but all playing the same music in the “downstairs” group. The group volume might still have a role to play there if I wanted to mute them all at once, or proportionally increase all their volume by a similar amount.