I recorded a midi track from my Yamaha MODX8 and can play it back fine through my MIDI interface/monitor while still connected to the keyboard. Once I unplug it from the keyboard I cannot play it on the iPad and hear it.
Thanks for your message and a warm welcome to the Cubasis forum!!
Our good friend Dom Sigalas created two dedicated clips, that explain how to make great use of Cubasis and the Yamaha MODX, which you will find below.
Hope that helps!
& enjoy being creative,