HELP I cannot make the Concert Level working

Hey Cyril,

First off, based on those specs, your computer is *NOT* the problem. ;-)

You can check under Mainstage->Preferences->Audio how many cores you have it set to use.

As to your other question. My technique is to ONLY put things that will stay the same through an entire concert at the Concert Level.
For me, that's usually only metronome, monitor mixes, and a reverb bus.

I typically organize as follows:
Concert Level- Things that will stay the same through the whole gig
Set Level- Things that will stay the same through a whole song.
Patch level- Things that apply to a section of a song (i.e. Verse/chorus/etc)

If you want sounds change, then add those at the lowest level that makes sense. Make the sounds be associated with a Patch can be convenient, because it lets you have "1 button" control over switching.

However, you could also set up a hardware controller to change settings within the same patch.
Remember, you can map any control to (almost) any function.

I would maybe think of it like this: If the new sound requires a different software instrument altogether, then just make a new patch.
If the new sound is just another setting within the same software instrument, then maybe just map the particular changes to your controller.

So if the mappings are the same, and just the sounds are different, then once you make the first patch including the mappings...then you can just copy and paste the patch to make a duplicate. (Click and hold on the patch in the list, then press option, and then drag underneath the patch to create an exact copy with mappings.)