The GPO4 download includes some VST expression maps for use with Cubase 5. Using them means you don’t need to fool around with keyswitches. Unfortunately Garritan's maps seem a little buggy at the moment - for a start they're generic which won't work because the octaves for the keyswitches vary from instrument to instrument. Edit: they're set up to work with notation instruments (see next post). The good news is that they are reasonably easy to adapt for the main instruments, I think!
I hope Garritan will soon come up with debugged versions. In the meantime, here’s how I managed to adapt Garritan’s version (for a solo violin). I make no guarantee that this is the best method - it's just how I managed to get things working. I use a PC but I imagine the procedure is the same for a mac.
You may want to keep a backup of the original files just in case! (on my system: C:\Program Files\Garritan\Personal Orchestra 4\VSTexpression maps)
You’ll need a track with the aria player on it.
The first step is to load an expression map (in the inspector, click on “vst expression”, then “no expression map”, then “VST expression map”. Then click on “load” and navigate to the VST expression maps in the Garritan program folder and pick the one you want.
Problem 1: The octaves are probably wrong. For instance, the expression map for solo strings has all the keyswitches listed as being in octave 0 and -2 but for solo violins they need to be set to 1. So … in the “Sound slots” panel click on the keyswitch note (“remote column”) and change it. For the violin example you would change the first keyswitch (called Arco) to C1 instead of C0. You also need to change the octave in “output mapping” (in this case from C-2 to C1). Make these changes for all the articulations (obviously keep the note the same as it was originally – just change the octave number).
Problem 2: To show up in Cubase editors, each articulation has to have a unique entry in the “Art 1” column of the sound slots panel. Delete all the entries in the Art 2 column. Then for each articulation: Click on the word in the Art 1 column and choose “Add custom articulation” from the bottom of the pop-up menu. Add a suitable description in the articulation panel. Alternatively, you can choose something more appropriate from the pop-up menu … but remember that you can only use each symbol once (and symbols picked from the menu show up on scores so they have to be appropriate!). I also changed the names of the articulations to match the ones in Garritan's manual.
Optional: There are two types of articulation listed on the articulation menu. “Direction” and “Attribute”. If you set an articulation to “Direction” it will act just like the old keyswitch system. If you set it to “Attribute” the articulation will attach itself to a particular note – it will only apply to that note and the next note will revert to the original articulation. Because I’m used to using keyswitches, I’ve set all the attributes to “Direction”. The disadvantage to that is that you can’t use the “info line” to pick them. (To change them you just click on the word “Direction” or “Attribute” in the Articulations panel.)
And finally, click save and save your adapted expression map under a new name.
To use the map, in the track inspector you click on “vst expression”, then “no expression map” and pick it from the list. (If it isn’t there you’ll need to reload it). See the manual for how to use articulations – for instance in the piano roll editor you can just open a controller lane (if you don’t see the articulations listed you need to make the lane bigger vertically) and then just draw them in with a pencil.
I hope this helps!