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In kindergarten and early primary school, children are taught scales as having steps and half-steps, or tones and semitones (T and S). This naming conveys that between one scale note and the next is always “one” something (tone or semitone, step or half step), indicating that these notes are consecutive in the scale despite their different size.
This is great for very young minds but doesn’t reflect how intervals are measured and described in general use.
The smallest unit of musical pitch (in Western culture) is 1 semitone. The semitone is a basic unit, like a millimetre. (Smaller units exist but they measure expression such as vibrato or micro-tuning rather than musical notes). Larger intervals are measured in semitones, not tones and semitones. We say an octave is 12 semitones, not 6 tones or 5 tones and 2 semitones.
(Personally I find that calling 2 semitones a tone is confusing, given that a “tone” is also the American name for a note as well as a word for timbre.)
I never refer to “tones” as an interval size in any of my writing. For scales, I write 2 or 1 (semitones) instead of T or S.
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This post is one of a growing series of holistic investigations into various aspects of music theory. The full list can be found in the Posts page under the category Music Theory De-Mystified.
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Most notes have at least two possible names. For example, F# is the same pitch as Gb. Even naturals have alternative names. E could be called Fb and F could be called E#. And that’s not to mention double sharps and double flats. G could be called Abb and so on.
Why so many choices? First, some background…
Modes
Major and minor keys are based on patterns of 2 and 1 semitone intervals between consecutive notes. We call such a pattern a mode. The series of notes generated by the mode is called a scale. Typical Western scales have 7 notes per octave, the eighth note being the octave of the first (hence the name “octave”).
The starting note of the scale is called the root note or tonic. The root note is easy to recognise when playing a scale because it is first and last. Melodies make the root note apparent by highlighting it in various ways so we can tell which mode we’re in when we listen to the music.
The choice of mode imparts an overall character to the music, called tonality.
Keys
A key is the combination of a mode and a root note. Keys allow us to choose the mode and the root note independently.
Let’s look at the major mode as an example. The original major, made up of only naturals, is C major. The name C major indicates that this key uses the major mode with C as the root note.
Any other major key needs at least one sharp or flat. By starting the mode on a different root note we need some different notes in the key to preserve the pattern of intervals from note to note. The pattern of intervals defines the mode, in this case, major.
We can work out the notes needed for a chosen key by placing the new root note at the start of the pattern and counting the semitones from note to note. Let’s look at D major; the major mode starting on D.
The note naming rule
There is one simple rule that determines the right choice of note name. In a standard Western mode such as major or minor, each scale note must have its own letter.
The letters indicate consecutive scale notes, just like they are written on a stave. A musical stave only has positions for notes as letters: sharps and flats are written as symbols beside the note.
When we work out the note names for a key, we start from the root note and count up. As we go, each following note must use the next letter as its name. In the example above, D major, the 3rd note is called F#. Gb is the wrong name because the third letter up from D is F, not G.
B#, Cb, E# and Fb
Remember BCEF? (see my beginner’s tip). This is the extreme end of BCEF. These notes look like they should never be used because they have equivalent pitches which are just naturals. B# = C, Cb = B, E# = F and Fb = E, so why use them? In truth their use isn’t all that common, but they do get used in certain keys.
For example, B# is used in C# major and Fb is used in Cb major.
This potentially begs the question, why use C# major as the name of a key when it could be called Db major? C# major has 7 sharps whereas Db major has only(?) 5 flats…
A valid question. I can’t answer it comprehensively in this post but there are three main reasons:
ease of playing/reading on a given instrument
movement within the piece from the home key to other keys
altered notes in the melody or chords
Easy keys
Players of some instruments such as guitar find sharps keys easier to read and play. Brass players, on the other hand, prefer flats keys. It depends on the base key and playing logic of the instrument.
Singers can be very specific about their choice of key for a particular song based on how the melody suits the different registers of the singer’s voice. This may force the rest of the ensemble to play in a key which is awkward to read, whichever name they choose.
For example, F# major has 6 sharps and Gb major has 6 flats. F# major has the note E# and Gb major has Cb.
Keys within a key
Typically a melody starts in the home key and goes on a journey. This journey takes it through various, usually related, keys, some of which are fleeting moments in the journey while others are visiting points; temporary homes. Campsites, if you like.
Visiting keys are named according to how closely related they are to the home key: in other words, how many notes they have in common. In general, if we start in sharps we continue in sharps, and the same for flats.
For example, in E major, a major key 2 semitones up would be called F# major, not Gb major. This is because F# is a note in the home key (E major) and Gb is not. In fact, none of the note names in Gb major are used in E major.
Which keys are related to which? That’s for another post.
Altered notes: weird note names in normal keys
Sometimes a melody or chord uses a note that doesn’t belong to the key. This could be as a variation or ornament, or the melody just might not be in a conventional mode.
We think of such a note as a replacement of the normal scale note or chord note. The context of the music determines which scale note has been replaced. To preserve the note naming rule, the new note is named with the same letter as the note it replaces.
if the altered note is a semitone higher than the scale note it is sharpened
if the altered note is a semitone lower than the scale note it is flattened
Sharpening or flattening allows the music notation to reflect which scale note is being altered, just as we would hear when playing and listening. However, depending on the key of the piece, this may require a double sharp or double flat.
NOTE: To avoid too much rambling I have only given a brief outline of the various topics raised in this post. I hope to cover some of these in future posts.
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Graphics taken from The Tiny Music Theory Book, a short, easy to read guide to the essentials of music theory and notation, available here.
