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A semitone or half step or half tone is the smallest musical relevant step (interval) in pitch that is used on most instruments and in (Western) tonal music.

An octave in this context is made up of twelve equal semitone steps.

#

name

ratio

0

prime

1:1

1

minor second

 

2

whole tone

 

3

minor third

6:5

4

major third

5:4

5

perfect fourth

 

6

diminished fifth

 

7

perfect fifth

3:2

8

minor sixth

 

9

major sixth

5:3

10

minor seventh

 

11

major seventh

 

12

octave

2:1

 

In written music, it is not immediately obvious what the interval is; the distance between two note-positions can vary.

Two notes both written on the same g-line can have distances ranging from zero to two. When allowing double sharps and flats the range extends to four semitones...

gb - g#

2

g - g#

1

gb - g

1

g - g

0

 

chromatic-intervals.jpg

Note-distance in semitones shown in red.

Scale position in blue.

 

See also:

     how to transpose music

     key

semitone
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