How would you do this...in iTunes you have to choose where to send the music? How do you select more than one?You can have external speakers and your iMac speakers working at the same time, but it requires an Airport Express base station with Airtunes and a spare set of powered speakers.
Then you can send music to both or either your internal speakers or the external ones via iTunes.
Probably not practical for what you want, but it is a solution!
There's a menu bar that appears bottom right of the iTunes window when you have multiple speakers connected. Clicking it brings up a dialogue box where you can choose which of all the speakers you have (including the Mac ones) to send music to.How would you do this...in iTunes you have to choose where to send the music? How do you select more than one?