When initiating music via voice control, the behavior of the Sonos Grouping of Rooms is now driven by the Preferred Speaker within the Alexa App Group - Please see:
Sorry for the long post but I've tried to explain some process, as well as some of the terminology for those first setting these up:
Alexa Group Set-up
Ques 1 – What is your Controlling Alexa Device?
1.1 – From your list of Alexa devices, both Sonos and others, choose the Controlling Device;
1.2 – Create an Alexa Group, named after the room that the Controlling Device is located in and select the chosen Alexa device. (If you select a Sonos device as the controlling device, this device can only be included as the Controlling Device in one Alexa Group);
Ques 2 – What Sonos devices do you want to reduce their volume on when Alexa is triggered (Ducking), so that the command can be heard by Alexa more easily?
2.1 – From your list of Sonos Rooms/Devices choose those that you want to duck when an Alexa Command is being given;
2.2 – Include all of these Sonos devices by adding them to the Alexa Group.
Ques 3 - What Sonos ‘Rooms’ do you want the requested music to be output on for Multi-Room Music?
3.1 – Within the Alexa Group set-up, select ‘Preferred Speakers’ and select all of the Sonos Rooms that you want to be grouped together for Multi-Room music.
3.2 – Save the Group
Please repeat for all other rooms which contain an Alexa Device that you want to control Sonos players.
1 - It is still advisable to create Groups, Devices and Routines with unique names.
2 - It is also possible to create an ’Uncontrolled Alexa Group’. In this case, an Alexa Group is created but with no Controlling Alexa Device (Ques 1) or Grouped Rooms (Ques 2) defined. These must be referenced with the Group name included within the command – See Scenario 2
Scenario 1 – Auto Group Sonos Players
Controlling Device: Echo Dot in Kitchen (Alexa Device name: Kitchen Echo Dot)
Grouped Sonos devices to be ducked: Kitchen Playbar + two Play:1’s as surrounds (Alexa Device Name: Kitchen Sonos), and Dining Room Stereo pair of Play:1’s (Alexa Device Name: Diner Sonos)
Preferred Speakers: All Sonos Rooms
Group Name: Kitchen
Start state: Only Kitchen Sonos playing music
Command to Kitchen Echo Dot: ‘Alexa, Play Soft Jazz’
1. Kitchen Sonos & Diner Sonos volume reduced on the trigger of hearing ‘Alexa…..’
2. Current music to Kitchen Sonos stops;
2. All Sonos Rooms group together and shown as such in the Sonos App;
3. Soft Jazz output to all Sonos Rooms
Scenario 2 – Play Music to a subset of Sonos Speakers from any Alexa Device
Controlling Device: N/A
Grouped Sonos devices to be ducked: N/A
Preferred Speakers: All Sonos Rooms Downstairs
Group Name: Downstairs
Start State: No music playing
Command: ‘Alexa, Play Soft Jazz on Downstairs’
1. All downstairs Sonos Rooms group together and shown as such in the Sonos App;
2. Soft Jazz output to all Downstairs Sonos Rooms.
Ques 1 – How do I play music to a single room?
Command – ‘Alexa, Play Soft Jazz on [Sonos Room Name]’
Ques 2 – How do I play music to my standard multi-room group of Sonos Players?
Command – ‘Alexa, Play Soft Jazz’
Ques 3 – How do I stop music being output to a single room (e.g. to answer the phone) but continue to play music in the other rooms?
Command – ‘Alexa, Mute’
This explanation is still in draft form, so please let me know if you have any questions.