I know, I know, nobody ever makes piano cake anymore. Mostly because it doesn't exist, at least not as a distinct Platonic ideal. But that never stopped us before, here at instructables.com.
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Now, it's worth asking, isn't this actually a recipe? I mean, making cake and all -- you eat it, right? To which I reply: It's only a recipe if I tell you what to put in it or how to cook it. This instructable is really a Play-With-Your-Foody, design-oriented endeavor. Quite edible indeed, but the key (har har) is achieving the appearance and design of a piano. I shall leave the baking and the caking as an exercise for the reader.

Step 1: Materials Needed

Needed:
- 1 rectangular (or square) cake or the ingredients&equipment to make one
- 1 pack of Keebler Fudge Sticks or knockoffs thereof
- 1 fine-tipped tube of black icing
- White buttercream frosting or the ingredients&equipment to make it
- Potentially 1 long knife (useful for any frustrating instructable, actually)

Step 2: First, Bake Yourself Some Cake.

Before you can turn a cake into a piano, you need to bake the damned thing. I recommend some easy out-of-the-box mix, since the cake is going to be covered in frosting anyway, and everyone's going to be so focused on the amazing likeness of a piano that taste will be of little to no concern. So really it doesn't matter much as long as you satisfy the following three criteria:
- Cakepan is rectangular or square -- NOT ROUND -- and please, no castles.
- Finished cake has enough structural integrity to hold up during frosting
- Do not make something so good you can't help eating it yourself. This is a presentation piece, after all.

One last thing about the baking: I should note that the finished cake need not be tall at all; in fact, the ideal height is just about an inch -- the height of a piano key. But any height will turn out very effective, so don't sweat it.

Step 3: Shape It Long and Low, Like a ... a ... a Piano Keyboard.

No matter what shape your pan was or how high your finished, cooled cake came out, it's time to cut into the rectangular shape of a piano keyboard. First and foremost, it needs to be flat on the bottom and flat on the top; I recommend one continuous cut with a long knife to remove any bulge from the top of the cake. Discard (read: Eat) the excised bulge.

Once you've done that, you need to transform whatever rectangular solid you're working with into a long, low rectangular solid -- the shape of a piano keyboard. Be creative here; I offer the following possibilities only as guidance.
- If the cake is still 2" high, make one continuous cut in a plane parallel to the countertop, using a long knife. Now you have 2 1-inch-high cakes that can be placed end to end to form a long keyboard!
- If the cake is square or squarish, make one continuous cut down the middle of the cake, in a plane perpendicular to the countertop and perpendicular to the edge of the cake. Now you have two rectangular cakes that can be placed end to end to form a long keyboard!

Step 4: Place Cake and Frost It.

OK, since you're about to frost this baby, you'll want to have it placed on the platter you'll be serving it on before we begin. Or at least on some foil-covered stiff cardboard so that you can move this thing once you've frosted it. Place your cake-halves from the previous step end-to-end, with the ends fully flush.

Now, open up your white buttercream frosting and cover this keyboard end-to-end. Note that this covers over any seam between cake-halves that you cut in the previous step. Be sure to frost as smoothly as possible; a long knife is helpful here again.

Step 5: Black-eyed Keys

Time for the black keys. Prepare to place one Fudge Stick on top of the frosted cake, with its short end flush with the long edge of the cake. Place this first one about 1 fudge-stick's width from the left end of the cake.

Now refer to a photo of a piano keyboard, noting that the spacing of these Fudge sticks is going to be a little irregularly regular. From the left edge of the cake, the sequence of spaces of Fudge-Stick width should be as follows:

{ open, occupied, open, occupied, open, open, occupied, open, occupied, open, occupied, open }

Repeat this sequence as many times as necessary, exactly the same way each time, and you'll have an outstanding set of black keys. If you only get halfway through the final repeat before you run out of room, that's totally fine, even for music-types.

Step 6: Danger: Black Ice! Ing!

Now comes the fun and dangerous part. No mistakes allowed from this point forward. You're going to draw in the boundaries between pairs of white keys, using that tube of black icing.

Between pairs of {open} spaces referred to in the previous step, this exercise is pretty straightforward: Just ice a straight line to divide the two {open} spaces evenly, all the way across the top of the cake and down the front (and the back, if you really really want to). I'd draw in all these {open/open} lines first, to give you a framework for the rest. Let's call these {open/open} lines baselines.

Now note that the remaining white keys all have slightly different shapes! Looking at the fourth Fudge Stick you laid down (fourth from the left, that is -- note name G#), the black icing should extend from the middle of the base of the Fudge Stick straight down to the edge and then down to the base of the cake -- easy enough. (Let's call this G# line a midline.) But for the two adjacent Fudge Sticks (F# and A#), the point of origin of the black icing should be halfway between the baseline and the midline -- NOT at the midpoint of the Fudge Stick.

A similar arrangement can be made for the first two Fudge Sticks you laid down. The lines you draw need to divide the space between the baselines into three equal parts, which means the point of origin of the black icing should be roughly at the 2/3 point (from left to right) of Fudge Stick 1 (C#), and at the 1/3 point (from left to right) of Fudge Stick 2 (D#). NOT at the midpoint of the Fudge Stick.

Again, repeat this pattern all the way up your keyboard and you'll be good to go. The goal is to have ALL white keys be of equal width lined up along the long white edge of the cake (the one not interrupted by Fudge Sticks).