The Proteus 2 is basically identical to the Proteus 1 except that it has 4 MB of orchestral sounds. A simple 4 MB ROM card of these orchestral sounds is available for the Proteus 1 too. Both the Proteus 1/XR and 2/XR models are enhanced modules with increased sounds and patches featuring up to 8 MB of sounds and well over 300 patches! The standard Proteus 1 and 2 could be upgraded to XR versions as well.