Monitor mono signal thru both stereo outs?

Good evening fellas…
Put the octatrack in the box and am trying to setup my AR with my MPC one. I also have a Moog little phatty. I have the rytms stereo outs going into the MPC and I have the Moog going into one (its mono) AR external input…

So far I cant get the Moog to come out both the stereo outs. I.E. I have to monitor the MPC’s ins on either the left or right channel to hear the moog in both speakers. This happens even when I have the AUD - set to only one channel. It technically works, but then I cant use the AR in stereo mode - like if I pan a hat slightly left or right.

what am i overlooking?

Thanks in Advance

a splitter has solved my problem…

OT could use the mono input and it would send out both outs…