A semitone is the smallest distance between two notes — the very next key on a piano (black or white), or the next fret on a guitar. A tone is two semitones.
Accidentals
An accidental is a sign written before a note that changes its pitch:
- A sharp (♯) raises the note by a semitone.
- A flat (♭) lowers the note by a semitone.
- A natural (♮) cancels a previous sharp or flat, returning the note to normal.
X:1
L:1/4
K:C clef=treble
C ^C D _E |
Here the second note is C sharp (a semitone above C) and the fourth is E flat (a semitone below E).
An accidental lasts until the end of the bar it appears in — the next bar line cancels it.
Remember
- Semitone = smallest step; a tone = two semitones.
- Sharp raises, flat lowers, natural cancels — each by a semitone.
- An accidental lasts to the end of its bar.