Heavy dust attracts moths!  The old rule is: A piano should be
disassembled, cleaned and moth proofed, every four years.

Piano cleaning involves removing the keys and vacuuming under them,
and also vacuuming the holes in the keys where they fit over the balance
rail, including the front rail bushings under the keys.  In addition,
all felts, once vacuumed, excluding the hammers, should be sprayed with
a non-reactive mothproofing spray, available from piano supply houses.
Use caution and mask any metal parts of the piano strings or action,
to protect from over-spray.  The use of compressed air works very well.
If the piano action is very dusty, it should be removed and taken
outside, when the dust is blown out.

In regard to the tracker bar, I have adapted a rubber nozzle for
a standard hand pumped tracker bar cleaner.  It is connected to a very
powerful vacuum cleaner (60 inches water gauge of vacuum).  Be very
careful that only the rubber nozzle touches the tracker bar, because
anything metal will scratch it.  Never blow air into the tracker bar,
always vacuum it.

Between the four year periods, about once a year, I remove the key
slip (the board in front of keys) and use compressed air and blow out
the dust from the interior of the piano and from under the keys.  Major
dust will drop to the bottom of the (upright) piano and can be easily
vacuumed out.  Grand actions can be removed and the cleaning done on
a work bench.

Bruce Clark