MidiKarval has released MidiMaster, a VST effect format plug-in that functions as a virtual master keyboard. Once connected in your host between the MIDI In and a multi-timbral VSTi or some VSTi set to different receiving MIDI channels, you can:

• Split your keyboard in two zones at a user definable point.
• Set for each zone: the transmitting channel, the Program Change message to be sent on this channel, the transpose (+/- 36 semitones, i.e. +/- 3 octaves) and the volume level.
• Save and load up to 10 of these settings and pass from one to another on the fly (useful in a live performance).
• Assign, in your host, all the knobs, sliders and the switch to CC messages, so that you can move them from your "real" master keyboard (if
  any).
• Switch off the split and use all the above-mentioned features on all the extension of your keyboard (the "right" section will become the "main" one.

MidiKarval costs €10. A demo version is available.