The musical alphabet: How notes in music are named
The term 'musical alphabet' is an informal term in music theory that refers to musical notes being named after the first seven letters of the alphabet.
In this system, notes are named in order of ascending pitch after the first seven letters of the alphabet, A B C D E F & G. Obviously there are a lot more than seven notes at our disposal, so the letters just repeat indefinitely as we continue to ascend in pitch. This is most easily seen on a piano keyboard where the white notes are laid out as:
ABCDEFGABCDEFGABC etc, etc.,
- until we run out of piano keys. So, every piano key is named the same as the piano key eight letters lower, (or higher) and we say that the relationship (or interval) between the two similarly named notes is an octave (from octo meaning 8).
Having so many different pitches named after just seven letters isn't a problem as the pitch differences are clearly shown by the unique positions of the notes on the music staff. There is also a convention of adding a number after the note name, such as C4, for example, to indicate the octave that any particular note name belongs to. Unfortunately, not all instrument makers or music software producers agree. While most refer to middle C as C4, some, such as Yamaha and a few others, refer to it as C3.
The differences in pitch (intervals) between the original eight successive notes that spanned an octave aren't all equal. In fact there are two such intervals. Originally, the intervals between A & B, C & D, F & G and G & the next A were (approximately) twice as large as the intervals between B & C and E & F. The larger interval is called a whole tone or simply a tone and the smaller interval is called a semitone. Many (if not most) Americans prefer to use the terms whole step and half step respectively for these intervals.
As music evolved, new notes were gradually introduced and inserted between those notes that were a whole tone apart. These notes correspond to the black keys on a piano.
Those new notes were named after their neighbours, with the addition of the word sharp (symbol: ♯) to indicate that the note is a semitone higher in pitch than its lower natural neighbour, or with the word flat (symbol: ♭) to indicate that it's a semitone lower in pitch than its upper natural neighbour.
Depending on the tuning system in use at various time in history, notes such as A sharp and B flat could be slightly different. The (relatively) modern tuning system known as equal temperament ensures that they are now exactly the same and that every note is separated from its neighbour by exactly one semitone, or half step, and that a semitone or half step is exactly one twelfth of an octave. In this tuning system, notes such as A sharp and B flat or such as C sharp and D flat, etc. have exactly the same pitch as each other and are said to be enharmonically equivalent.
Sharps and Flats
Pitches can have more than one name. For example, the black key note that sits between the white key notes, A and B, can be called by either of two names. It can be called A sharp because it's a semitone higher in pitch than A (but not as high as B) or it can be called B flat because it's a semitone lower in pitch than B (but not as low as A). If there's no musical context, then it doesn't matter whether we choose to call the note A sharp or B flat.
You can also see on the piano keyboard that there are no black keys between B & C and between E & F. This is because those pairs of notes are already only a semitone apart, and so it wasn't necessary to try to squeeze any new note between them. This applies to all pitched instruments, of course, not just the piano.
As mentioned above, if there's no musical context, we can choose to call the 'in between' notes by either the flat or sharp name. However, if there is a musical context, then there are strict rules about the correct name to use in any situation. In fact, in music theory, any natural note can be made sharp or flat, and there are contexts in actual music or scales where you can see notes being called B sharp, E sharp, C flat and F flat. Of course, these are just special naming conventions derived from historical contexts; B sharp and E sharp now sound the same as the notes C and F, respectively, while C flat and F flat sound the same as B and E, respectively. There are even musical contexts that call for the use of double sharps or double flats. None of this is relevant to our discussion though, except to inform you that the names do exist and not to be confused or surprised if you come across them.
The 12 Pitches per Octave
If we lay out all the note names in music in order of pitch, we have the full musical alphabet representing the twelve notes that span an octave.