MIDI patches only getting synth sounds

Your old GarageBand Jam packs should still work. How did you migrate to Mt. Lion? Did you use Migration Assistant? Then probably your Instruments Library has not been copied properly, see Christoph Drösser's post:

Migration doesn't copy Instrument Library

To fix this, copy the Instruments Library from the folder on your old mac

/Library/Application Support/GarageBand/Instrument Library/

to the corresponding folder on your new Mac.

But i did hear about mainstage 2. how does that integrate with GB?

MainStage 2:

All five JamPacks in MainStage 2 will be installed at exactly the same locations that GarageBand uses. All Loops and instruments are fully compatible and you do not need to do any set-ups or additional installations to use these from GarageBand. It is really a good deal, if you compare it to theearlier prices of the JamPacks.

There are only a very few instruments that seem to have changed the names. Occosionally I find a drum, that has changed the name and I have to change the instrument, but I find that not very dramatic.

Regards

Léonie

Which will mean my old jam packs won't work cos they're PPC (at least that's what the research i've found seems to say).

The installers and documentation for some of the old JamPacks are Power PC applications, and do not run on Lion or Mt. Lion, but the Jam Packs itself are only media files and data files, not programs - they work with Mt. Lion. But to transfer them, you have to migrate your old system or to track down all fles in the system library, that contain Jam Pack media.

You need to transfer all files from the System Library in

/Library/Application Support/GarageBand/

and also all folders with loops in

/Library/Audio/

Also, you may have to rebuild the Loop Index, see: Rebuilding the Loop Index in GarageBand

It might be easier to invest in MainStage 2; this way I got two additional JamPacks that I not yet had.

Regards

Léonie