Accidentals

In music there are what is called accidentals. These consist of sharps, flats and naturals. When we look at the keyboard, we notice that there are black keys and white keys. An F sharp is the black key directly to the right of the F white key. A D sharp is the black key directly to the right of the D white key and so on. An A flat is the black key directly to the left of the A white key. An E flat is the black key directly to the left of the E white key and so on. A C flat is the same as a B, a B sharp is the same as a C. An E sharp is the same as an F and an F flat is the same as an E.

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In the picture below there are examples of sharps. They look like #.

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In the picture below there are examples of flats. They look like b.

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In the picture below there are examples of naturals. We can see the flats b, sharps # and the other symbol is the natural which cancels out a flat or sharp. This means that a Bb would become a B and an F# would become an F.

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An accidental only affects the notes in the bar as in the example below. The end of the bar is written as a vertical line. This piece of music is one bar, so every G note in the bar would be G#. The subsequent bars would be back to G.

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In the picture below the accidentals apply to every bar. The E and the B are flat throughout the piece of music because two flats are written at the start of each stave on the E and B position. This is called a key signature.

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There are also double sharps which are written X and double flats which are written bb. A double sharp is raised a tone for example, an A double sharp is the same as a B, and a D double flat is the same as a C. 

Warburton, Annie O. Basic Music Knowledge. Cambridge: Cambridge University Press, 1995. Print, pp. 27 and 28.