-- non-subscriber, please reply to sender and MMD --

The lowest four notes are supposed to be blocked on Duo-Arts, but my
notes 1 and 2 play along with accompaniment 1 and 2 , whose holes are
positioned above.  Why isn't the rubber hose being blocked?  Notes
3 and 4 seem to be working okay.

Can anybody advise me on what to check first?  Could it be something
in the black box underneath the tracker bar pneumatic with 18 hoses
attached?

Regards,
Ian Sanderson