Many readers will remember a Tom Hanks movie from 1988 called "Big".

In the movie a young boy gets supernaturally transformed into a twenty-something man and finds out what it's like to be big.

Perhaps the most iconic scene of the movie has two of the characters dancing on a scaled up "Big Piano"- that's the scene everybody seems to remember.                                                                                                               
They turned the movie into a Broadway musical and later licensed the show to be performed in community theatre. My local community theatre (South Valley Civic Theatre in Morgan Hill, California) decided to do "Big the Musical" as a teen show, and the production staff approached us to build a Big Piano that could hold its own next to the movie version and give our show a "wow" moment.

Not many people need to build a Big Piano, and if you do it's likely you'll have specific goals and constraints different from the ones we faced. This instructable is less of a detailed plan and more of a set of notes explaining the problems we were trying to solve and the way we chose to solve them. I hope other Big Piano builders can learn from our experience.

Step 1: How Big is the Big Piano?

The width of a piano is determined by human ergonomics and the pitch range of the music you need to play. In this case the piano has to be danced on and that means a white key big enough for a human foot to step on. That is: about 7" wide. The music the characters play on the piano has a 3 to 4 octave range. We went for four octaves. ie- 28 white keys, each 7" wide. We added 6" end caps to the piano So the overall length was (28 x 7) + 12 = 208".

The depth of the piano is more flexible. We wanted our piano to approximate the proportions of a real piano, and that's about a 7:1 depth to width ratio for white keys. To keep things simple we went for a overall depth  of 48".

The height is also flexible. We decided to light up the front of each key with a square of light. With some additional height details we ended up with an overall height of 12".

So all together the design target was 17 feet long, 4 feet deep and 1 foot high. That's big!

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