From an inquiry I made to Amazon:
'd like to inform you that, external speakers connected via Bluetooth and the Alexa Voice Remote for Echo do not currently work during Multi-Room Music playback. However, you can listen through external speakers, as long as those speakers are linked to an Echo device in the group using a wired connection.
*Also, please note that, when listening through a Multi-Room Music group, all the devices in that group access the same stream and play the same title simultaneously. There is no such option to stream different music on each device in a group separately, or listen through more than one Multi-Room group at once.
*Also, I'd like to inform you that you can't add an Echo device to more than one Multi-Room group. If you want to add a device to a new group, you need to remove it from its existing group. Open "Settings" > "Multi-Room Music" from the Alexa app menu, select the group, and then uncheck the box next to the device you want to remove.
I've forwarded your suggestions to our Alexa development team and they'll look into this and come up with the possible options available. However, we cannot promise if these options can be implemented on the device.
Whenever there is a new feature or any enhancement, an update will be rolled out.
If you need any additional assistance, I request you to contact us from the below link and we'll surely help you,
http://www.amazon.com/amazondevicesupportSo basically, if you create a group (as I did) called "downstairs" consisting of 3 dot's and an Echo, and ask to play some music, they all play. BUT, and it's a big but, now they will ALWAYS all play. You can no longer play something on just one. Plus, if any of them are connected to a BT speaker, that connection no longer works, they just play on the dot. The only way to just play something on one is to go to the app and remove it from the group. So basically, until this gets fixed (send your cards and letters folks) this is essentially useless; at least to me.
Jim