.
I have a 'generative music' program that creates Brian-Eno-Type stuff. It puts out GM to the system's onboard soft synth. It does not give me access to the MIDI code it creates.

What I want is an app that will capture the MIDI data into a form where I can manipulate it in, say, RealBand. Do any of y'all know of an app that can do this?

You probably already have the program - RealBand! You should be able to route the MIDI if it actually has MIDI output. It's hard to determine if it does do this or not based on your description. Can you send the MIDI somewhere besides the program's own internal synth? If so, just port it to RealBand. Then look at the Event List on the recorded MIDI and see what is there to manipulate.

If you can't break out the MIDI from the generative app, then you might have to resort to using Jack or the like. http://jackaudio.org/

What is this software called?

I might be able to help if I knew it's name.

Without knowing the particulars, I have had a similar problem with MusicNotes music. They have a proprietary "midi" format that can only be read by their own midi player. No way to save or export as .mid - and that's what I wanted to do.

I installed a "virtual midi cable" like midi-ox or LoobBe1. Then the player saw Loopbe1 as an output and I selected it. Using Sonar (I'm sure RB would work), I selected LoopBe1 the track input to LoopBe1. I armed a Sonar midi track to record and started recording. Then went to the player and started to play the midi file - and like magic - all the midi data came pouring out of the player into Sonar through LoopBe1. When done, I had to drag all the notes in the Sonar track to the correct start time since there is not much start -time control in this approach. I saved as .mid, and done.

kelso has the better tip. I couldn't remember the MidiOx program name and could only come up with Jack (I realize that to some that reads funny!)

I used MIDI Ox a very long time ago. I don't have experience with LoopBE, but this sounds like just what you might need - if you can route from the generative program.

Or maybe Paul's plugin ..

http://www.pgmusic.com/forums/ubbthreads.php?ubb=showflat&Number=191662&page=1

People round here are pretty cool sometimes.
Seems like it might be something that could help 'capture the midi'. If it hits the synth plugin his app may reroute it for you.

Look for the most recent version. He improved it from the initial release.

midi-ox and -yoke are great - but a bit cantankerous, imho. LoopBe (also free) only does one thing, so it's pretty easy to manage - even I can do it.