The minor second interval is when two notes are played 1 semitone apart.

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1 semitone = 1 guitar fret and/or 1 key on the piano

The most well-known use of the minor second interval is in the score to the movie Jaws.

What does a minor second sound like?

The minor second interval is a tense-sounding interval.

This is what it sounds like, played one note after the other.

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When the two notes are played together, it creates a lot of tension. This is what it sounds like when both notes are played together.

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How I use a minor second

Minor second intervals occur in pretty much all of the most common scales (major and minor), so I use them all the time in chords and melodies.

BUT!

When I am using the interval for its intrinsically tense character, I use it when writing horror music, because I think it is one of the three scariest intervals in music.