The secondary Alchemy studio G4 Mac can be run locked together with the main ProTools machine, running a separate set of programs such as Logic or Ableton Live, Reason or any of the other current soft synths, etc..
There's a large range of available software.
(too many to list) but includes:
Logic Pro 8 (+jam packs)
Pro Tools Le 7
Ableton Live
Cubase
Reason 4
Easy Drummer (all)
Kontakt 2
Reaktor
String machine
Absynth
Native Instruments, (B4, Pro Five, Pro-52,Battery) etc
Guitar Rig
------And many others------
Full compatibility with any Midi Hardware you bring in...