Layering Tracks/Voices

I have a Pro~One and an MS-10 hooked up to the CV/gate voices. I can play each from the KSP keyboard on different tracks, and I can split the KSP keyboard and have one synth on the lower half and the other on the upper half by holding down the two track buttons at the same time.

What if I want to play both synths at the same time? e.g. play a note on the KSP and trigger both the Pro~One and MS-10 at the same time on the same note. Is it possible?

I have assigned Track 1 to Voice 1 and Voice 4 using the CV Routing, but this results in round robin playing of the two synths, but curiously, only when I play legato! When playing staccato it only plays Voice 1.

Cheers.