Settings to get the Steel Drums and Marimba to sound with the tremolo.
I have set the Marimba voice into R1 and the Steel Drums to R2 just for demonstration.




Now press "Direct Access" button and then the Harmony/Echo buton to get this screen.

Scroll down to "Tremolo". I set mijn to 16 for the tremolo as it sounds OK to me.
Use the same settings for both drums and Marimba.




Now press Registration Memory button and make sure that the Harmony box is ticked.





Go to Functions and pick Registration Sequence, tab to Freeze and tick the harmony box.





All set for the tremolo sounds. The Harmony/Echo button must be ON for the effect.



Den