Amazon is rolling out the capability for Bluetooth speakers to now be included in Music Groups. Prior to this update, this was not possible.
To create a Music Group, use the latest version of the Amazon Alexa app, go to Devices, tap the Plus sign at the top of the page, and choose “Add Multi-Room Music Speakers.”
If this ability is not working for you, check to see if a firmware upgrade is available for your Echo device.
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