Jeff Evans
If two synths (even different models but same manufacturer) are on the same midi port and they are set to the same channel then they will both respond, end of story. As I have said only midi channels will separate any number of instruments (same maker or not) that are on the same midi port. 
 
But where ID numbers and device ID's are good though is you can just send s SYSEX dump of say a memory bank to all of them and only the relevant machines will respond which does make it easier in that regard only.
 
Its not that great though to have too many synths on a single midi port. Even though in theory 16 different instruments/parts can operate on a single port, as midi is a serial protocol the delay is longer for each synth. eg approx 1ms per channel so if 16 instruments share one port and you want them all to play at once the last one will be 16 ms late. Noticeable.
 
The ideal situation is to have only 8 or less instruments and put them all on their own port (8 x8 interface) and get them to do a max of 1 or 2 parts at once. That way you will get super timing everywhere. Even with only two parts per port 16 tracks of music is a pretty big sound in any case. At some point you are going to need to transfer midi parts to audio anyway leaving them free to do either nothing or another one or two parts max.
 
 

+1
 
Excellent clarification of the issues at hand.
 
Especially true about timing get flaky during congestion - it's a 31K serial port after all. It does make me wonder, though, about USB based midi devices. There's no such built-in limitation there. No worry for my traditional midi-port based trusty old MU80 though, it'll flake long before the the port capacity goes with it's limited 32 note polyphony... sigh..
 
 
 
 

There are good implemented MIDI synths and badly implemented MIDI synths.
This link is just about MIDI though and not the other article that referred to badly implemented synths. (it was written in 1995, so maybe things have changed.)(Roland was good, Yamaha was bad. ??)
 
http://www.midi.org/aboutmidi/tut_midimusicsynth.php
 
Have fun though.
 
I guess this is it then perhaps:

http://www.sweetwater.com/store/detail/MidiExp128/

The Express 128 provides eight MIDI ins, eight MIDI outs, 128 MIDI channels, and compatibility with all Macintosh and Windows software. And, if you ever need more, it's expandable to over a thousand channels via a powered USB hub.

Going Bonkers over MIDI (sounds like a title to a new song perhaps).

 
Bonkers over MIDI!
 
 

hahaha.

+1 MOTU midi express XT

I have an old Ensoniq KMX8 MIDI patchbay I picked up for a few bucks at a fleamarket. 8 ins, 8 outs. You simply press the button of the input that you want to route, and then the button of the output you want it to route to. Couldn't be simpler. I don't know what I would do without this device.

I remember the KMX8 - a wonderful MIDI patchbay! I had one for a bit (I lived outside West Chester, PA, so I had one of almost everything Ensoniq made up through the ASR<G>). Eventually I outgrew it, though.

Right now I have a Digital Music MX-8 that I use to route all my controllers. I like the MIDI processing, although these days I tend to do all of that in Sonar. Still nice to have around!
 
Then I have one JLCooper Synapse and two JLCooper MSB-1620s, as I've been whittling down the hardware I've already dispensed with the need for one of the MSB-1620s. I'd love to get down to just the Synapse, but it didn't happen this time around.
 
I also have a Yamaha MCJ8, which was is real simple 8x8 MIDI Patchbay, no processing, no nothing, that I kept in the guitar rack. It too is headed for eBay.

Not sure how I feel about the continuing down-sizing of my MIDI rig<G>...

My favorite midi box is the Kawai MAV-8, if you can find one you'll appreciate the instant patching and visual feedback. It's straight up 4 in 8 out all on large switch sliders. One of the inputs and one output are in the front panel so instant patching for quick set-ups and tests are easily and immediately available. I can't tell you how fundamental that is when you need to patch something in quickly. No little back lit screens or software to set-up. 4 inputs has always seemed to be plenty for me.

Not sure how I feel about the continuing down-sizing of my MIDI rig....
 
Bill it is OK and it gets better over time   I had 53 keyboards at one point and as many rack mounted things. Now I have got it down to 5 pieces of hardware only plus two extra computers just being virtual instruments. And on my main computer something like 100 VST's.
 
The reality is there is almost nothing you cannot replace with a VST these days.  (Analog included)  Tell my what you think you cannot replace and I bet I have got a solution for it.
 
Hardware wise I have a Kurzweil PC3K now with Kore 64 installed and really it almost replaces everything on the planet!  A K2000R which I don't use that much.  A EMU E5000 sampler with a huge Emulator, Akai, Roland, Ensoniq libraries (it can read em all and it sounds great still to this day)  A Roland JD800 which is a bit unique (and has a terrific panel for sound design) and a Roland JV30 . (best GM sysnth that allows great and fast editing of GM sounds)
 
With all that gear I had before I am still doing now what I used to do without loosing anything, in fact my setup is better now.  (Alchemy and Wusikstation have almost got it covered between them alone!)
 
You can do it! I am just down to one patch bay now with 8 ports on the back.

ok... I'll bite...
 
Can't replace my ARP 2600 - tried the Arturia, did not like it, tried the TimewARP, loved it, but it is not quite the same, so I'm keeping the hardware.
 
Can't replace my MS-20 - I have the Korg plug-in, and it is cool, but it is not the same.
 
Still have found nothing that sounds like the Ensoniq ESQ-m or the Roland MKS-80. I would love to find something to replace these. NI FM-8 is really close, sometimes even better, than the TX7, but I have not been able to reproduce some of my favorite TX-81z patches yet.
 
The Kurzweil 1000PX - no, not terribly realistic, but terribly cool, and I've yet to find a replacement.
 
I am happy with a handful of EPS/ASR and S900/S1000 libraries that I have successfully imported into Kontakt, but it is a LOT of work to import them. It remains quicker to just use the old samplers.
 
Other than that...
 
I'd say the old Pro-53 does a great job of covering various Sequential sounds. If I could get another Prophet 5 I'd probably buy it<G>!
 
The Oberheim Matrix/Xpander family - I can't find anything that covers them, but all I have is the Matrix 1000, and frankly, it doesn't do a great job of covering the Xpander either<G>!
 
So... fire away! I'd love to empty another rack or two, and put it all up on eBay (well, except the ARP and Korg<G>)

There is the less expensive MOTU midi express 128 (8X8 and USB). It's fine if you do all your midi routing inside your PC. Sonar will do just fine merging inputs and sending to multiple outputs. The 128 does not have buttons or internal patching and doesn't do standalone midi routing. But if you're just recording multiple inputs and playing multiple outputs, it's a no-brainer.