For example, suppose you play an F and an F#, or a B and a C, from the same octave at the same time. It usually doesn't sound very good. I've looked a while but I can't seem to find a name for it. Is there a name?

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    If you are looking for a word to discribe it and not a technical name I would go with dissonance or dissonant. – b3ko Sep 28 '18 at 16:53

Generally you would call these intervals minor seconds. But depending on the "spelling" of the notes you could call the interval an augmented unison.

B and C is a minor second

F and F# is an augmented unison (the letters are the same so it is a unison to start, then the sharp on the second F augments it by making it 'bigger' by a half step.)

These intervals are considered dissonant and harsh sounding.

  • so, if it sounds terrible normally, why does it sound decent when used from different octaves? eg: in a song called "eisoptrophobia," the bass note is F#0, and the melody note is G2. why do different octaves sound good vs. same octave? – CrashRocks1419 Sep 28 '18 at 17:42
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    It does not always sound horrible - it depends on context. There are fabulous examples of the use of the minor second in Bach and Mozart and many others. – JimM Sep 28 '18 at 19:15
  • @CrashRocks1419 Keep in mind that a minor second and a minor ninth aren't the same interval (although from a chord identify perspective they are the same pitch class.) For me, the minor ninth is much less dissonant than a minor second. Also consider the perception of dissonant intervals when the two notes are played by difference instruments. The dissonance seems softened when two difference instruments are involved. I image all this can be explained acoustically as simpler wave forms or interval ratios. – Michael Curtis Sep 28 '18 at 19:57
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    Interesting. In Jazz, a b9 is generally considered to be much more dissonant than a b2. Standard teachings suggest that you should avoid a b9 on any non-dominant functioning chord but you could include a b2 without subverting the function of a non-dominant functioning chord. For example, if you voice a minor 7 chord with a 9 and place the 9 and b3 next to each other, it creates a beautiful sound but if you were to place the b3 an octave higher, creating a b9 interval between it and the 9 of the chord, it sounds pretty trashy and subverts the function of the chord. – Basstickler Sep 28 '18 at 21:19
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    Isn't this normally just called a "semitone"? – SaSSafraS1232 Sep 28 '18 at 23:14

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