The _old_ pianos were made with lumber core wood.  The lumber had cross
banding and then veneer on top of the cross banding.  Most old uprights
in the 'twenties and 'teens had wormy chestnut for the core wood.  In
most instances the cross banding was poplar.  The veneer was thicker
than most veneers available today.

We regularly get calls to pick up old upright pianos for free.  They
are usually not worth the effort and not worth the expense to restore
them.  I use these old pianos for the wood to make my cases.

In extreme circumstances I plane these piano parts to the wormy chest
nut or cross banding so I can re-veneer them with the veneer of my
choice using hot hide glue.   I order veneer from Certainly Wood in the
thicker sizes.  They are 1/16-inch thick, two feet wide, and six to
eight feet long.  Order more than you need as the quarter sawn is a hit
and miss situation.

In later pianos the lumber core is poplar wood which weighs more than
wormy chestnut.  Many of the pianos made today use the poplar core wood
such as Steinway and Yamaha.

Lumber core wood is available from several suppliers.  Certainly Wood
has these sheets and can add the veneer of your choice.  I typed in
"Veneer" in the web search engine to find suppliers.

Don Teach