Iím new here on this forum but do own a BR1600. You could send the main outs or headphone outs from both machines to a basic mixer. If you donít have a mixer, there are inexpensive options out there for around $100 that would work. You could also send the main outputs of one machine into two inputs on the other machine.
Happy Roland-Boss guitar, synth and multi-track gear user since 1988!
Current Multi-tracks: BR1600CD, VS1824CD, VS1880, BR600