To control external instruments within Cubase you must use Scaler as a VST plugin and route Scaler’s MIDI output onto the track of the instrument you wish to control.
How-To
- Load Scaler VST onto an instrument track and the instrument you wish to control on a second track.
- Change the MIDI input of the track you wish to control to Scaler - MIDI Output
- Arm Scaler track so it receives MIDI from your controller and turn on the monitoring on the controlled track.
- Scaler MIDI output is now routed to your instrument.
PDF version: Scaler - External Instrument Control Setup - Cubase 9