Jerm, thanks for taking the time to follow my problem, and Scooterman, many thanks for taking the time to share your advice. You've both helped me narrow down the problem somewhat. The bottom line though is that after many hours banging my head at this, I still have no sound from Unity within Metro SE.
I've gone over every suggestion several times. This is what I did to make sure that my Audio MIDI Setup works:
-Even when there is no sound from Unity within Metro, I can use my external MIDI keyboard (hardware) to trigger sounds in Reason 2.01 as well as in Unity in standalone mode (running without Metro open).
-I can also trigger Unity's sounds when Metro is open and I open one of Unity's applications--Mixer, Keyboard or Player--(they all play sounds, but function differently). I can confirm that Unity doesn't receive MIDI from Metro because even though I can trigger Unity, which is running as a separate application outside Metro, when I record MIDI within Unity and play it back, there is no sound from Unity.
-I've tried all the option in the MIDI menu located on the lower righthand corner of the Transport.
-None of the keyboard keys on the lefthand side of the Graphical Editor trigger Unity.
-My best guess is that there is an interapplication MIDI problem here, at least when I can confirm that audio is working by successfully playing imported audio files.
However
.....
I'm having problems with sound output from Metro in general. Jerm, I did that test you suggested, and imported a sound file to check the audio output. It's erratic, sometimes it works and sometimes it doesn't, and I can't even begin to pinpoint a reason. This has been going on for days so I can't say it's my imagination anymore.
Once, an audio file played successfully but when I stopped it and played it again after about a minute, all of a sudden there was no sound. I pressed the metronome button to see if that would work. It did, for about half a minute, then it stopped working too.
I'm sorry to bring these problems up but I've really checked everything I can on my side.
It's entirely possible that the main problem lies with Unity because I've had many problems with previous incarnations of Unity 3, but I'll save those stories for some other time. However, I can't explain the sudden loss of audio. I use my 12" powerbook's built-in audio so there are no soundcard drivers to blame.
I apologize if this post is a little rambling, but it's 2:18am in Singapore and I'm a zombie. Thank you for all the help you've already given so far. At the very least, I understand how Metro works with MIDI and audio now so hopefully my problems are no longer related to my ignorance.
This shouldn't be this difficult. I'd have given up hours ago if it weren't for the fact that I'm dealing with Unity. I'm used to having to go crazy before I can get it to work. This is a new major release (3.1.0), and 3.0.0 wasn't usable until 3.0.5.
Now if only there was Rewire support, then I could try Reason with Metro, which usually works the first time with everything.