Hi All,  Removing the tubing in the (what I call) "wrap-around"
Duo-Art upper section is an extremely easy task.  There are two metal
connectors (at the extreme right and left ends of the top action)
that are held to two other metal connectors via a single leaf spring
(on each side).  Each spring is held in place by a moveable 'latch',
which is located at the front of each of the metal connectors.  The
spring is released by pulling the latch forward.

However, here is a note of caution.  Do not simply pull the latch
forward and watch what happens.  You might get quite a surprise.
Instead, press down slightly on the forward leading edge of the spring
just aft of the latch.  Then, while holding the spring stable, pull
the latch forward, and then gently release the tension on the spring.

Once the tension is released, you will find that the spring is quite
loose, and it is easily pulled out of the piano.  But, note that there
is another piece of metal which looks identical to the latch and the
other end of the connector.  As you will discover, this piece of metal
is actually a guide for the connector as well as the securing point of
the far end of the spring.

After the spring has been removed, you should be able to lift the
connector 'up' without any problem.  However, this is not always the
case.  If the connector has never been removed before, it could be
stuck because of the leather gasket that provides the seal between the
two adjoining metal connectors.  If that is the case, do not get out a
prying tool and stick it between the two metal pieces.  That will only
serve to damage the metal.  Instead, take a slender, triangular-shaped
piece of wood and use it as a sort of chisel.  NOTE: Only employ this
method after you are convinced that you cannot separate the connector
by pulling, pushing, or otherwise 'manhandling' the upper connector.

The point of using a wedge (to pry the piece apart) as a last resort
is that you don't want to damage the gasket if possible.  Making a new
gasket, which may end up being an eventuality, it not an easy task.

Musically,
John A Tuttle
Player-Care.com
Brick, New Jersey, USA