I have an alexa, and a heos (heos not hooked up yet, planning stages now). Does anyone know how alexa plays music on the heos? for example if I say "alexa, play pandora in bedroom" will alexa set my heos device to pandora, and start playing it? or will alexa stream her audio to the heos, and the alexa actually does the streaming etc?
you have to connect the Heos to the Amazon Echo through the skills setting in the Alexa app. once you do that, the Alexa will send the commands to your Heos device to activate whichever app you want it to.
you can and should use specific command words in Alexa that help it to work best. Doing music app through Alexa can be frustrating as Alexa wants to default to doing this stuff itself. so be specific in your wording like "Alexa, tell HEOS to play Pandora" which should work. a command like "Alexa, play Pandora" will just have the Echo play music through the alexa speaker.
when you have it all connected and working, the alexa just sends the command to get the HEOS working and that is what will do the streaming.