Yamaha RY9 Owner's Manual page 32

To select Chord Root or Chord Type, press [ E ] and [ F ]. The flashing
indicator will be positioned above the currently selected one.
To change the backing Chord Root or Chord Type, press [+1] and [-1],
followed by [ENTER] to lock in the new chord.
Chord Root
To exit Chord Assign, press [CHORD] again.
SELECTING THE BACKING ACCOMPANIMENT.
The backing accompaniments consist of Bass, Chord 1 and Chord 2 tracks,
preprogrammed to match the relevant Preset patterns. You cannot modify a
backing, but you can select a different backing to temporarily play with the
currently selected pattern.
To select a backing accompaniment, within the Pattern Mode Pattern Select
function, press [ E ] to move the flashing cursor over the backing name in
the LCD; the backing name will begin flashing, indicating that you can select
a different backing accompaniment to play with the currently selected
rhythm. (This is a good opportunity to hear how the different backings
sound with different rhythms!)
The patterns, number 192 through 199, don't contain bass and chord data.
Chord Type
24
ENTER