It will somewhat work with the 1.03 firmware. I used to have the 1.03 firmware in my MKS-70 but have upgraded it to 1.08 (paid for by Roland!!!). You will have to put up with a few minor annoyances for this to work with your unit. The most noticeable problem you will have is lack of real-time parameter changes only for Tone B (it will look like it is updating Tone B, even the Tone B number indicator flashes on the unit, but it is actually updating Tone A). You can get around this Roland flaw by turning off "AUTO SEND" when working with Tone B. When you are finished making your adjustments to Tone B, press the "SEND" button which will send a SysEx message which will actually update Tone B instead of Tone A. I have changed the interface from the PG-800 considerably as I believe Roland didn't provide the most ergonomical interface for this unit. My goal wasn't to make something which looks like the PG-800. Instead my goal was to create the most useable and responsive programmer which controls PATCH factors as well (not completed, but you will see I have started this). My sliders are quite functional. I also used push buttons instead of cogged sliders where I could for easier access to those parameter settings. You will probably be impressed that when you select a PATCH on your MKS-70 with the JX-Editor running, all tone parameters will automatically update as well. There is a MIDI Through setting in the MIDI Setup screen which will allow you to play your keyboard as you try out sounds. I also included a sound slider to try out the sounds as well. Use the "Kill Last Note" to turn off the note when finished.

Keep in mind that this application is totally in Beta testing/development stage and still needs significant work. I haven't released a manual for this either. I wanted to give it away for free to benefit others.