To understand the layout of the traditional piano's 88 keys we must explore a bit of both music theory and history. I know! A real attention grabbing opening, right? But wait. If you aspire to play by ear or be able to identify what musical devices you are being served on a daily basis in your favorite songs and be able to recreate them, you need this information. So here we go. We will get the hard part out of the way by putting it second. We will take a look at the theory first.
There are only 12 unique notes in the theory of music and the same is true on any piano. All other notes are just copies of one of those 12, just in a different octave. That means every set of these 12 unique tones makes up an octave. On the piano, these 12 notes are given one of two colors. 5 of them are black, and 7 are white. Understanding both how these keys compliment and differ from each other and how these relationships change in different octaves is vital not only to the aspiring pianist but to any serious musician.
The white notes are named:
A, B, C, D, E, F and G.
Don't get lost, yet!
The black notes are a little more complicated. Remember there are only 5 of them, okay? Here they are:
C#, Db, D#, Eb, F#, Gb, G#, Ab, A#, Bb.
Wait, that was 10 notes. What happened? Well...Each black key on the piano has two names. They can be identified by the white key directly above or below them. They are either called a sharp of the of the white key below or a flat of the one above. So why all this extra naming? Why not just have a unique name for each black key?
Now, its a bit different to many musicians who play by ear, who often refer to "shapes" or "landmarks" on the keyboard that serve to guide their ear and fingers to the right white or black keys and for them, all the extra identification seems like a waste of time. But the super-short version is this: every black key having 2 names is necessary because spelling is just as important in the reading and writing of music as it is in any language. With all the different tonalities, scales and chords that are at our disposal, we must clearly identify what is happening on the staff if we are to successfully store, distribute and receive musical ideas. This goes much deeper but that is where I'll leave it for now.
Alright 7 white keys. 5 or 10 black keys. That is the octave in a nutshell for today. 12 unique notes. So then why are there 88 keys on the piano? Well, how many octaves is that? 88 divided by 12 gives us 7 octaves plus a few extra notes. That is a pretty wide range! As a single instrument, the piano's range compared to all other instruments is very generous, stretching both below and above the limits of the human singing voice. No, parlor tricks don't count! Many instruments can reach lower or higher than a piano but not many can do both. Of those that can, the pipe organ would be the most notable. Strings and woodwinds as a family can beat the piano both high and low but not with single instruments. The brass family wins on the low end but stops usually somewhere in the 7th octave depending on how many trumpet players are in the same room. Pitched percussion outstretches the piano on the high end but not the low end. The organ is basically king of the single-instrument range wars.
My take is this: At a fraction of the size of an organ, and giving up a mere octave at both the low and high end of commonly used notes among all instruments, the 88-key piano, for its entire history, has offered perhaps the most accessible creative pallet available to the composer, the singer, the arranger and the solo performer.