I assume here that you'll not be using MIDI for VCO 3 and that you want separate control of just VCO 3 (from VCO 1 and 2) when the synth is being played.
You can use Expression 1 or 2 on the back of the synth as CV inputs. These are available as sources in the bottom two rows of the matrix. Lets' use Expression 1 in this example
- Assign one of the user assignable mod matrix columns, say #13 to VCO 3 Coarse
- Assign Exp1 / M3 to column 13, so that Expression 1 will now control the pitch of VCO 3
- Switch off Kbd Track for VCO 3, so that it will not follow the keyboard/sequencer/arp
- Adjust the Mod Amount of the Exp1 / M3 to column 13 assignment until you have the pitch tracking right
- Adjust VCO 3 coarse to set the tuning
The last two steps requires a little fiddling. Play alternating notes at an octave interval and adjust the Mod Amount until VCO 3 plays that same octave interval. Use the VCO 3 Coarse knob to adjust the pitch bias. Repeat this until VCO 3 tracks the octave interval and is at the right pitch.
The Expression inputs accept 0V - 3.3V so it'll cover 3.3 octaves if you use a standard 1V/oct CV. The Expression inputs use the following connections: Tip = pot center tap; Ring = 3.3V; Sleeve = Gnd. So use a TRS cable with the ring unconnected, your CV connected to the tip and ground connected to the sleeve.
