If System is SMS
C3 (note on FM7) = Bassdrum / kick. works only FM7 chanel.

all other drumkits notes will be played on FM8.
examples
C#3 (note on FM7) = will be played on FM8 even if chanel FM7 is muted.
F#3 (note on FM7) = will be played on FM8 even if chanel FM7 is muted.
F#3 (note on FM7) = will be played on FM8 even if chanel FM7 is muted.

Drumkit on FM1 -> FM6 is silence
Drumkit on FM9 will be played on FM7 , FM8

test notes on FM9 , C3,D3,C#3,F#3
if FM7/FM8 unmuted, C3,D3,C#3,F#3 will be played.
if FM7/FM8 is muted, D3 will be played.
if FM9 is muted D3 is muted too.

should it be that way ?