Kourtney Kardashian & Travis Barker Make Out in Studio, MGK Forced to Watch

Kourtney Kardashian and Travis Barker want everyone to know they are still very much into each other ... and seem to have a preferred PDA pose.

The reality TV star and the rock star found a new spot to hold each other and make out -- Travis' at-home music studio -- and Kourtney documented the occasion ... adding heart and fire emojis for extra measure.

The pics are reminiscent of the steamy shots of the couple kissing in the desert a couple months ago ... the main difference being that Kourtney's ass is much less visible.

There is one other difference too -- for this round of Kourtney & Travis PDA ... it seems Machine Gun Kelly was an innocent bystander.

In the second pic Kourtney posted, fans noticed the singer's in the background in a recording booth ... possibly laying down some new music. Now, he and Barker are buddies, but ya gotta wonder if MGK consented to bearing witness to their hookup.

BTW -- Travis replied to Kourtney's post with "My baby" ... along with his own heart and fire emojis.