Why Piano Keyboards Have Different Types Of Keys

Diatonic Scales Versus Chromatic Scales

Have you ever wondered why a piano keyboard has mostly large white keys, along with a number of smaller black keys, raised above the level of the white keys?

It's the sort of question a kid might ask, only to be dismissed by an adult with an answer like, “That's just the way it is.”

But it's a legitimate question, though few people can answer it.

As with so much of music, it has evolved over the course of hundreds of years, and most everything has to be backward-compatible (meaning we don't want to make music from the past be impossible to play or read, going into the future).

On early pianos, claviers, organs, and harpsichords, the color scheme (black and white) wasn't necessarily what it is today. Also the numbers of keys in the keyboards varied. But still, the smaller raised keys in-between the larger keys were there – probably from the beginning.

In this article, we will explain why this came to be, and lead you through an experiment to find out why there are different types of keys.

Here is a picture of a traditional music keyboard, showing the white keys, along with a smaller number of black keys (in-between the white keys):

Notice that wherever two white keys are next to each other, is where there is a half-step between the notes (as labeled in the diagram). Everywhere else (where there is a black key between the two white keys), there is a whole-step.

Notice also, that the letter-names of the keys (to the left of the keyboard diagram), use only the letters A through G (A, B, C, D, E, F, and G – there are seven of them). The pattern repeats itself, going up or down the keyboard.

Notice that if you start with any white key (counting it as number one), and count white keys, upwards (or downwards), over eight keys, that key (number eight) will have the same letter-name as the key we started with (number 1). Try it, using the diagram above.

Notice that the letter-names correspond only to the white keys, and the black keys have no letter-names. Why is it this way?

The music we are used to listening to in our culture, is built on a diatonic scale, which has seven distinct tones (numbered 1, 2, 3, 4, 5, 6, 7, and starting over again on the eighth key (going again to the number 1).

The fact that the eighth key away from any given key has the same letter-name (is a higher or lower version of the same note) is where the term “octave” came from (octo = 8). But there are only 7 distinct tones in a diatonic scale, each with its own letter-name. The eighth note is the same letter-name note, starting over again.

Here is how Wikipedia defines a diatonic scale:

In music theory, a diatonic scale is a heptatonic [seven tone] scale that includes five whole steps and two half steps in each octave, in which the two half steps are separated from each other by either two or three whole steps, depending on their position in the scale. This pattern ensures that, in a diatonic scale spanning more than one octave, all the half steps are maximally separated from each other (i.e. separated by at least two whole steps). The word "diatonic" comes from the Greek διατονικός [diatonikos], meaning progressing through tones.

The seven pitches of any diatonic scale can be obtained using a chain of six perfect fifths. For instance, the seven natural pitches that form the C-major scale can be obtained from a stack of perfect fifths starting from F:


Called Pythagorean tuning, this property of the diatonic scales was historically relevant and possibly contributed to their worldwide diffusion because for centuries it allowed musicians to tune musical instruments easily by ear.

Note: The text surrounded by [square brackets] are comments I inserted, and the yellow background text, I highlighted, because it is important.

It's easy to hear the note an octave (the eighth note up from, or down from – the same letter-name note) a given note, and tune it so that it is perfectly in-tune with its other note. It is easy to tune two such notes by-ear.

Likewise, it is almost as easy to tune two notes, where the lower note is numbered 1, counting up (white keys) to number 5. Any two such notes can also easily be tuned by-ear. In other words, it's almost as easy to tune a 5th interval, as it is an octave interval.

If you start with an “F” note (number 1), note number 5 up from it is a “C” note. Continuing, if you start with the “C” you ended on (as number 1), note number 5 up from there is a “G” note.

If you tune “F” with the “C” above it, and then that “C” with the “G” above it, and then that “G” with “D”, and then that “D” with “A”, and then that “A” with “E”, and then that “E” with “B”, you have tuned all of the notes of the diatonic scale.

I'm sorry to hit you with a lot of music theory, but it probably explains why so much of the music we listen to in our culture is based on a diatonic scale.

But what about the black keys?

If you start with any letter-name white key, and count both white keys and black keys, up to (but not including) the next same-letter-name white key as we started with, you will get a total of 12 keys. These 12 distinct tones between any two same letter-name notes, are the notes of the chromatic scale, also referred-to as a 12-tone scale.

Diatonic scales are built on the chromatic scale.

Here is our keyboard diagram again:

You can begin to see that a traditional music keyboard is actually a graphical representation of the different diatonic scales.

Major and minor scales are different versions of a diatonic scale. They differ in where the half-steps are in the scale.

For a major scale, if you number the keys, starting with a “C” letter-name note as number 1, upward to the next “C” note (which will be number 8), the half-steps will be between numbers 3 and 4, and 7 and 8. Likewise, a minor scale (starting with the “A” note) has its half-steps between 2 & 3, and 5 & 6.

There are also modal scales, such as the Dorian mode (or “Russian Minor”), starting with the “D” letter-name note, with its half-steps between 2 & 3, and 6 & 7, or the Lydian mode, starting with the “F” letter-name note, with its half-steps between 4 & 5 and 7 & 8.

There is a different modal scale starting on each letter-name note. All of these modal scales are different versions of a diatonic scale.

If you play only white keys, you will automatically be playing a major, minor, or modal scale, depending on which white key the scale starts with. Tunes, and music in general, are based on all these diatonic scales. Diatonic scales are built on the chromatic scale.

If you play only white keys, you are playing a tune based on a diatonic scale. If you use a black key, it is not a note of a diatonic scale, and is called an “accidental”. In a tune, if you use a note not in the scale, it is an “accidental”. Accidentals can sound good in a tune, and give it variety, but they are not typically used that often. Most notes in a tune will use a diatonic scale.

But musicians, being creative and inventive, didn't want to use just the white keys. Also, a major (or minor) scale's tune, using just the white keys, may be out of the range of a particular singer.

You can make a major or minor (or modal) scale start on any note (including black keys) as long as the half-steps and whole-steps are between the right numbered notes of the scale.

For example, if you want to play a major scale starting on the “D” note (which would be the Dorian mode if you played all white keys), you simply play (instead of the F) the black key above the F, called an F-sharp, and (instead of the C) the black key above the C, called a C-sharp. This keeps the half-steps in this scale between note numbers 3 & 4, and 7 & 8, which is a major scale.

To remind the musician which notes to “make sharp” in this major scale, key-signatures were invented. For example, the key-signature for the key of D-major has two sharps (the F and the C), and looks like this:

The center of the “#” sign is (in both the treble clef and bass clef) centered on the “F” note's line, but it indicates that every “F” note needs to be played a half-step higher ('sharped').

Likewise, the center of the “#” sign is (in both the treble and bass clef) centered in the “C” note's space, and is a short-hand reminder that every “C” note needs to be 'sharped'.

With the piano (or any standard music keyboard instrument), you need to practice scales in each of the possible key-signatures so that you can instinctively play the correct sharped or flatted notes for that key-signature.

With the KeyMusician Keyboard, on the other hand, it always plays in the specified key-signature, so the only time you have to flat or sharp a note, is when it is actually an accidental (a note not in the current key-signature). And often, such notes are required by the particular chord used, so the accidental is inserted into the melody keys, and the melody note is flatted or sharped automatically.

So with the KeyMusician Keyboard, there is no need to practice scales at all, since it takes care of key-signatures for us automatically.

There is another reason for the raised keys on a traditional music keyboard that has little to do with diatonic scales. That reason, is that when you're playing from music (and thus not looking at the keyboard), you can 'feel your way' along the keyboard, to know where you're at.

Now that we know all of this underlying music theory, let's try an experiment to see why there are different kinds of keys on a music keyboard, discovering the need for ourselves.

With the KeyMusician Keyboard, there are no smaller raised keys (for the notes between the notes of a diatonic scale), and we don't need them because the software normally plays the notes of the specified key-signature. So with this instrument, all of the keys are the same.

There is a way to set up any performance pane so that it plays the notes of a chromatic scale (instead of a diatonic scale). Note that the music display doesn't show it properly because it isn't a very useful thing to do. So for the sake of this experiment, we ignore what is shown in the graphics display. If enough users request it, we could implement a chromatic scales display mode.

This experiment is like taking a piano keyboard, and everywhere there was a black key, replacing it with a white key, and now, you're going to try playing music with it. Are you excited to give it a try?

First, let's hear the difference between a diatonic scale, and a chromatic scale.

Click on the links below to hear a full-keyboard glissando in first a diatonic scale, and then a chromatic scale:

Diatonic Scale Glissando

Chromatic Scale Glissando

Notice that with the chromatic scale glissando, the notes are closer together, and the range between the highest and lowest note (played at the end) is less than with the diatonic scale.

Playing in-key-signature (the notes of the diatonic scale) is what gives the KeyMusician Keyboard its impressive range, using just a typing keyboard. You play the sharped (or flatted) version of a note in a process similar to typing a capital letter in an e-mail. But usually, you don't have to play such notes at all – it does it for you.

Now, let's try improvising music in a chromatic scale.

All you have to do, is (in the performance pane you want to use, but not the Drums pane) click the “Percussion” check-box (to the left of the KeyMusician.com picture), to set it.

To play all of the percussion instruments (which are assigned to each of the notes of the chromatic scale within a certain range) the KeyMusician Keyboard needs to use the keyboard keys to play the chromatic scale notes. This mode is turned on by selecting the “Percussion” check-box, as is the display. But the instrument being played doesn't actually need to be a drum-kit, in which case, you're playing a melodic instrument in chromatic scale mode.

As mentioned before, in this mode it does not show the music notation right (because, as you will see, it's not a very practical way to play the instrument). But you'll get a chance to try playing in a 12-tone (chromatic) scale, with all keys being the same (there are no raised black keys).

So here's a screen-shot of the performance pane I used (I liked the Space-Voice sound for this strange music):

When you select the “Percussion” check-box, it sets the “Base Octave” spin-control to 3, and the “Transpose” button to “-1 = 5-sharps”. And the display is set for percussion – so ignore the display. But where it's playing the “Space Voice” sound, it's playing it in a chromatic scale.

Give it a try on your own KeyMusician Keyboard.

It has a strange sound, and you fairly quickly find that you need to skip certain notes to make it sound decent. Most of those notes you find you have to skip correspond to notes not in the diatonic scale for (in this case) B-major.

You can play chords if you like. Again, you will find that a lot of notes in the melody section need to be skipped-over in order for it to sound good with the chords.

So, in summary, what an amazing invention it was, to have the black keys that you skip over, playing the white-keys diatonic scale!

An Improvisation Example

Some modern composers (such as Arnold Schoenberg) really like 12-tone (chromatic) music. I am not one of them, but my likes aren't the only way to enjoy music.

In improvising this piece, I first found a chord I wanted to end on, and a chord to start on. The rest of the piece is wandering around musically, trying to get to the ending chord.

I'm clearly not very good at it, but if I liked that type of music, I'm sure I would get better at it with practice.

Give it a listen by clicking on the link below. See what you think.

Improvised 12-Tone Music

I hope this article was interesting, informative, and useful for you. - Aere

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