For both the small and the grand piano, we will use the 4 available types of folded cloth. The different types are referred to as cloth A, B, C and D as in the picture.   You can dye the cloth as you work, but if you have no black dye tub of your own, you can use pre-dyed cloth (which makes stacking and locking down a bit harder).  I use undyed cloth in the examples for clarity.  All items are dyed black.

The small piano

- First, place a writing desk, back side facing south
- Place 3 spacers on top of it (fish steaks, black pearl, etc.)
- Place 2 of cloth C on it
- Place a wooden crate on top.
- Inside the crate, place 1 chessboard, 2 of cloth A, 2 of cloth C, 2 of cloth A , and another chessboard

(You need 2 piles of cloth A, and 2 chessboards because the stacking order of items is not always the same, as you will see later on.  The 2 piles of cloth A are colored differently to demonstrate  this)

- Now drag the desk onto your spellbook in your pack. It should snap back, but the other items will now be lowered.
-  Lock down the desk and cloth.
Let the black pearl decay.

- Destroy the crate.   You will see one chessboard, and one pile of cloth A.
- Lock down the 2 C cloth, and the visible chessboard and A type cloth

Now, walk outside your house (step off the porch completely) and walk back in. Repeat until you see the different colored cloth A  (or when your cloth is pre-dyed, single click until you see that the visible chessboard is not locked down). 
- Lock down this cloth A and chessboard as well.

- Place 2 of cloth B, and 2 of cloth C on top
- Drag the stack of cloth B onto your spellbook and let it snap back. Lock both down

- Place another 2 of cloth C, and 1 cloth A and lock down

The Grand piano

This consists basically of two small piano's with some extra stuff.  We will be building this in four tiles, which are referred to as tile I through IV as shown here.  The tiles are built up in numerical order.

Tile I:

- Place a writing desk, with the back facing south.
- Place 3 spacers on top of that, and a crate.
- Place 2 of cloth C, and 2 of cloth D inside the crate.
- Drag the table onto your spellbook and let it snap back.
- Destroy the crate, lock the cloth down

- Place another crate on top
- Place 2 of cloth C, and 2 of cloth D inside the crate
- Drag the table onto your spellbook and let it snap back
- Destroy the crate, lock the table and cloth down

- Place 2 of cloth C on top
- Place 1 cloth D on top
- Lock everything down

Tile II:

- Place three fancy shirts and lock them down

Tile III: (continuing with black cloth)

In this tile we start by building a small piano, but after placing the table, place a body sash underneath it (here shown in red for clarity).  Then build the rest of the small piano as usual.

- Place a fancy shirt on top of the stack
- Place an oilcloth on top
- Drag the fancy shirt onto your spellbook and let it snap back
- Lock the shirt and oilcloth down

It's beginning to look like something!

Tile IV:

- Simply build another small piano in this tile

And we're done! 

Some variations (for whcih I didn't have time :-)

- Try letting the tables decay, and build the piano legs using hats (bonnets) dyesd black
- Try building pedals out of something.  Someone suggested a tall candle for the pedal pillar