Natural means to forget about sharping or flatting a letter or note, just play it normally (naturally). The B you are playing stays a B. The F you are playing stays an F. The same goes for every music letter or note.
You know the difference between a higher and a lower sound. But how much higher is going up a half step(#), or how much lower is going down a half step(b)?
For a half step up: A to A# is the (guitar) fret between A and B. So, we hear that there isn't much difference in sound between a half step up (#) or a half step down(b).
B to Bb is the next (piano) key going down from B natural. The half step is relative to the natural note's name it goes up(#) from, or down(b) to, landing a half step from the natural note (like natural C to C#, or natural E to Eb).
Furthermore, to flat a note that's already sharped, and vice versa, make the note natural, since we're stepping up or down to the note. These half steps are like stairs.
You might be asking, 'What happens after I get up to G? Where do I go from there?' You should go right back to the letter A. Or, 'Is there a step between G and A also?'
Yes. Between B and C, and between E and F (Bake Cakes, Eat Food), are the only exceptions where there are no between steps. The rest of musical letters have steps between. So it looks like this:
... and so on. We learned earlier, that in sound, Steps are either flat from the note above, or sharp from the note below:
I'll refer to these letters as notes you can hear. Again, if the step between is sharp, it takes on the lower note's letter (A to A# going up). If it is flat, the step takes on the higher note's letter (B to Bb going down).
This is logical, because a sharped note SOUNDS higher than the previous note. Likewise when you flat a note, the note SOUNDS a half step lower from the note you flatted (B to Bb).
To simplify: One key up from A on the piano is A#. One key down from B is Bb. Notice that A# and Bb are the same note. We call this kind of note an Enharmonic, explained soon.
Before, I labelled the placeholder between natural notes as 'steps'. We now see there is a half step before the sharp or flat note, and another half step after the sharp or flat note. So there's a whole step between the natural notes (except bc,ef).
Scales are important, because they use notes in a way that sound pleasant to the ear. There are many different types of Scales, but we will focus on just one, called the Major Scale.
It's the type of scale that is used in most music today, and sounds like the musical phrase, 'Do Re Mi Fa So La Ti Do'. You would have a Major Scale, if you were to play:
Notice how the scale ascends the letters of the alphabet, ending on the same note it started, with 8 letters total. However, should you start with a different alphabet letter, not all of the notes would be played in their natural state; some scale notes would either be sharp#, or flatb.
In fact, some Major scale notes would fall in-between the letters. This is because of the sound. We want all Major Scales to have the same basic sound pattern, no matter on which note we start. The starting note (root) will not sound the same for different Major scales, but the basic, overall sound pattern of the whole Major Scale is the same.
You remember a sharp and flat are half steps up or down, from a note. And two half steps added together makes a whole step between two notes.
Remember, B to C is a half step, and C to C# is another half step, making a whole step between B - C#. The full scale step pattern has 2wholes, 1 half, 3wholes, then 1half steps, or,
This pattern of steps works for every letter on which you may start a Major Scale. It makes a phrase of sound (scale) from any note you start. You can play it backward or forward, starting and ending on the same note.
Here's the A Major Scale, with the steps removed:
Why is there a whole step between some of the letters? To explain, A to A# is a half step, and A# to B is another half step. So, add those two half steps together, and you'll get a whole step from A to B, in our scale above (A h A# h B).
Again, F# to G is a half step, and G to G# is a half step. So, F# to G# makes a whole step (F h G h G#). It is easier to play the steps on an instrument, so you can see, as well as hear this scale pattern.
The Sharp Flat Rule page has more Major scale explanation.
Has it occurred to you that if a Sharp and a Flat both land on the same (half) 'step' between natural notes, two different notes must be named? This is true, even though these sharp and flat notes have the same sound:
The notes A# and Bb are the same note, and G# and Ab are the same note.
A# = Bb , G# = Ab
While these between steps have two different names, one sharp and one flat, each tone is the same. It is the same sound, because both refer to one note. This note with two different names, but one sound, is called an Enharmonic.
Why does it have two different names? The key of a song will determine which sharp or flat enharmonic appears. We may use either note, depending on whether the melody goes up in sound (sharp), or down (flat).
Now, we may say that there are two (half) steps between two notes. Because from one note to the flat or sharp tone is a half step, and from the flat or sharp tone to the next note is a half step. For example, D to D#, then D# to E are two half steps. The opposite direction is E to Eb, then Eb to D:
D h D# h E , E h Eb h D
To be thorough, scales going up may have flats, such as the Eb major scale:
Cro-magnon wha? Chromatics is just a fancy term for all half steps, either up or down:
C C# D D# E F F# G G# A A# B C (for sharps)
descending: G Gb F E Eb D Db C B Bb A Ab G (for flats)
Both of these are examples of a chromatic scale. Music uses half steps for sounding sad (down), or excited (up).
Chromatics have only half steps, differing from Major Scales that have both half and whole steps.
Additionally, Chromatics smoothly transition between scales and musical phrases we play in a melody. This is due to chromatic graduations, or half step intervals. Basically, an instrument's frets, keys, or vocal leaps may allow an easy chromatic rise or fall into another scale or phrase. Half steps, up or down, are small note changes to quickly find another scale.
In the next page, changing a scale's first note forms keys, which have combinations of half and whole steps.