Amazon's Alexa app gets more Sonos-y with new multiroom audio controls - The Verge
Amazon's new multi-room Alexa music feature lets Echo devices work in concert; Sonos, Bose and others coming soon – GeekWire
My Media for Amazon Alexa
The Best Multi-Room Wireless Speakers
How to set up and use Amazon's Alexa multiroom music - The Verge
My DIY rack-mountable Alexa multi-room audio system : r/alexa
Amazon.com: Audio Pro Addon C5A Smart Speaker | Alexa Built-in, Smart Home Speaker | Multiroom, High Fidelity, Compact, Wireless Bluetooth Speaker | Also Good for Outdoor, Home, Camping, Travel, Beach | White : Electronics
Amazon.com: WiiM Mini AirPlay2 Wireless Audio Streamer, Multiroom Stereo, Preamplifier, Works with Alexa and Siri Voice Assistants, Stream Hi-Res Audio from Spotify, Amazon Music and More : Electronics