Tones, semitones and accidentals

In the previous lessons we talked about the staff, the clefs and the notes. But not everything fits inside the 7 note names we know (C, D, E, F, G, A, B). Between them there are even smaller distances, and there are symbols that let us write them. This lesson completes the basics of pitch, before we move on to how time is organised.

01The smallest distance: the semitone

In Western music, the smallest distance between two notes that we use is called a semitone (in American terms, a half step). Two semitones together make a tone (a whole step).

The easiest way to see it is the piano. Two neighbouring keys (white-white or white-black) are always one semitone apart. When you skip over a key in between, you cover a tone.

Inside one octave (the distance from one C to the next C, or from any note to the same note one octave higher) there are 12 semitones: 7 white keys on the piano and 5 black ones. This is the foundation of the Western musical system.

02Where the natural semitones are

On the piano, the black keys do not exist in every gap between the whites. Specifically, there is no black key between E and F, and none between B and C.

That means E → F and B → C are semitones all by themselves, with no symbol needed. All the other neighbouring notes (C→D, D→E, F→G, G→A, A→B) are a whole tone apart.

E · Fsemitone

B · Csemitone

03Accidentals: sharp, flat, natural

To raise or lower a note by one semitone, you use a symbol called an accidental. There are three basic symbols:

• Sharp (♯): raises the note by one semitone. E.g. F♯ is the black key between F and G.
• Flat (♭): lowers the note by one semitone. E.g. B♭ is the black key between A and B.
• Natural (♮): cancels a previous accidental and restores the note to its natural position.

The three basic accidental symbols

Sharp

+ semitone

e.g. F → F♯

Flat

− semitone

e.g. B → B♭

Natural

cancels

e.g. F♯ → F♮

Two important observations:

• The same black key on the piano can be named in two ways. For example F♯ = G♭ (one key, two names). Such notes are called enharmonic: they sound the same but are written differently. Which name we choose depends on the scale and the harmonic context, and we will discuss it in Chapter 4.
• Among the accidentals you may also meet the double sharp (𝄪) and the double flat (𝄫), which raise or lower the note by a whole tone. They appear rarely, in more complex music and in specific harmonic situations.

04An accidental lasts for the whole measure

When we write an accidental in front of a note, it does not apply to that one note only. It applies to every later appearance of the same note within the same measure (bar). The barline cancels it, and the next measure starts clean.

See how it works in a 4/4 example:

05On the bouzouki

On the bouzouki (as on every fretted string instrument), the semitones map directly onto the frets. Each fret is one semitone higher than the one before it, and every two frets make a tone.