I've worked through this in several ways and it isn't currently possible to play mp3 files or YouTube videos in Ultra. There are a couple of ways to share the visual from YouTube (either open a separate browser session and share it or embed a video in a power point file and share it) but there is no way to play the sound through the blackboard session. Since both mp3 files and youtube videos are essential to my course materials, I will be using Blackboard original this Fall. Ultra will have to wait until they add the multimedia functions. I'm interested in know if anyone else uses these files in a synchronous online course or if you feel that playing the sound through Blackboard is essential for an asynchronous course.