Roland MT-32 detected, but not working. What's wrong?

[Tigerfog]

Hi, everyone.

I just bought a Roland MT-32 used off Ebay.
I got it all plugged up, but things are not working out and I would like some assistance in pinpointing the exact source of the problem.

I have a USB-MIDI cable, which has one light for IN and one light for OUT. They seem to to light up when there is activity from the Roland MT-32.

And so, as it seems I should do, I took my USB-Midi cable and:
-plugged the cable's IN end into the OUT socket of the Roland MT-32
-plugged the cable's OUT end into the IN socket of the Roland MT-32
-plugged the cable's USB end into my Macbook's USB port.

I power up my Roland MT-32, configure my scummvm to CORE-MIDI and REAL MT-32.

I run Monkey Island 2 and the Roland MT-32 actually responds appropriately with instruments' names displayed in the MT-32's mini screen and channels being active. Also, the "OUT" light on my USB-MIDI cable lights up constantly, indicating some activity.

However, there is NO output of music.
I don't hear any music from my speakers.
The "IN" light of my cable does not light up.

When I unplug the cable's "IN" end from the MT-32's "OUT" socket and plug it into the Roland MT-32's THRU socket instead, the "IN" light of my cable lights up, but of course, I don't hear anything out of my speakers.

So now I'm wondering:
-Is it safe to say without doubt that the cable's not the faulty one here?
-Could it be that the Roland MT-32's "OUT" socket is not working as it should be?
-Was there another cable that I should've used as well, like the OUTPUT MONO (L) socket of the Roland MT-32?
-Is there another way for me to get anything out of my Roland MT-32?
-If my Roland MT-32 is the faulty one, should I open it and try to repair it? Is it safe to do that? How complex would it be to attempt that?

I'm counting on your help! I haven't given any review for the seller of this MT-32, so if it turns out that it's Dead-on-arrival, I will deal with him.

EDIT: Also, I just tried to plug my headphones directly into the Roland MT-32 and only then I can hear some music.

EDIT #2: Maybe I was wrong with how things are supposed to work? The midi music goes from the PC to the MT-32, but it cannot go from the MT-32 to the PC? Is that how it works? If yes, does it mean I'm supposed to go buy speakers and plug them directly into the Roland MT-32 to enjoy my old games?

[Pix2]

The MIDI cables only carry MIDI instructions which is why you can't hear anythimg. You also need to run an audio cable between the mt32 and your MAC from the l and r output sockets to your line in.

[Tigerfog]

Thank you for the information.
I'm a bit of a n00b when it comes to audio equipment, so I didn't know how things work.
Seems like it's time for me to go get some TRS connectors and maybe a new set of speakers.