I'm used to playing the 7th and 9th with the 11th in an X11 chord, hence the Bb and D for C11. Strange that Yamaha don't offer a way to play this chord, to me at least.
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Graham, Korg Pa1000, Korg G1 Air, Countryman E6, Roland BA330, 2 x Roland CM-30, , Mackie SRM150