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Every interval can also have an augmented (and diminished) version.

Is that true about augmented (and diminished?) unisons? As in C>C♯, and C>C♭? I ask, as C>D♭ is m2, as is C>B, but that's only the same in sound and one semitone distance between. Intervals have two criteria - note names and distance apart.

Edit - as requested. My question asked both about aug. and dim. unison. And - it's elicited some interesting thoughts - hasn't it?

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    Yes, C -> C♯ is an augmented unison, and C -> C♭ is a diminished unison. What is the question here? Melodic intervals also have another criteria: direction. Commented Feb 8 at 12:18
  • @ElementsInSpace - question - do they exist? Is that what they're called given the examples in the question? Can't find them in my theory books. Don't comment - answer!
    – Tim
    Commented Feb 8 at 12:31
  • To some extent, it really is as simple as “augmented“ meaning “made bigger” and “diminished“ meaning “made smaller.“ So you can have “doubly augmented“ like C -> C##. There’s no reasonable use for “triple sharps,“ but if there were, I suppose there could be such a thing as “triply augmented.“ Commented Feb 8 at 14:07
  • @Andy Bonner I think Bbb - Cx would be a triply augmented 2nd? No need for a triple sharp!
    – Laurence
    Commented Feb 8 at 14:18
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    @ElementsInSpace The interval C - C♭ is an augmented unison. You can augment an interval up or down. In both cases an increase in distance has happened. Examples of augmented thirds: C - E♯ and C♭ - E. You can also dimish intervals up and down. Examples of diminished thirds: B - D♭ and B♯ - D. There is one interval which can not be diminished and that is a unison because you can not decrease the distance. Commented Feb 8 at 15:35

3 Answers 3

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Augmented unison is definitely a thing. C and C#. Nothing weird about it.

Diminished unison, well... would be kind of the same as augmented unison, only you'd think of the two tones in reverse - instead of "from C, a semitone up to C#", or even "from C#, a semitone down to C" (which is still the same augmented unison), you'd now have "from C#, a negative semitone up to C".

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    Could be, as aug. is opposite to dim.
    – Tim
    Commented Feb 8 at 12:33
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Sure, the system extends to unisons. An augmented unison is straightforward, you just decide to spell a semitone as C to C♯ rather than C to D♭. The diminished unison may be more of a theoretical entity, it's difficult to see why anyone would want to see C - C♭ as a diminished unison UP - but the system allows it.

(Possibly - just possibly - this sort of analysis might open the door to new and interesting music. Sort of like the square root of -1 in mathematics and physics. Unreal, but useful. I'm listening...)

Other opinions are available.

"Some theorists do not allow the diminished unison because the C flat lies below the C natural and this breaks the[ir] rule that all dyadic intervals are named from the lower note."

https://simple.wikipedia.org/wiki/User:Sonia/Diminished_unison

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    The interval C - C♭ is an augmented unison which should be rather clear I would say. Augment means "make greater" or "increase" and the interval C - C♭ is in fact bigger than C - C. I mean it doesn't matter whether you augment upwards or you augment downwards. Commented Feb 8 at 16:27
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    @LarsPeterSchultz I HOPE you're just fooling with us! But as your comment got a +1, guess I'd better put you right. In music interval-speak, 'augment' means 'bigger upward'.
    – Laurence
    Commented Feb 8 at 20:31
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    No fooling here. I have never seen a music theory book that would restrict augmented intervals to only mean bigger upwards. That would make no sense. An augmented interval is defined as an interval that is one half step larger than a perfect or a major interval. The enlargement can be up or down. An example of an augmented third could be A♭ - C♯. On this particular augmented third you don't even know whether it is enlarged upwards or downwards. Like is it A♭ - C that is changed upwards to A♭ - C♯ or is it A - C♯ that is changed downwards to A♭ - C♯? It is an augmented third either way. Commented Feb 8 at 21:30
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    @LarsPeterSchultz There is a problem of translation and language-dependent terminology, actually: In Czech for instance, the only equivalent of "augmented" is really "zvětšený" (literally "enlarged") and it always is meant upwards (unless you specify the direction in which you mean the interval). And we quite carefully distinguish "zvětšený" and "zmenšený" (literally "diminished"). I would never call C - Cb augmented, to me that's just simply diminished.
    – yo'
    Commented Feb 9 at 11:58
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    @Laurence Dimished first is not a theory, it appear in music already in baroque, and in a way even sooner, and it's the key ingredient to a descending passus durisucullus.
    – yo'
    Commented Feb 9 at 11:58
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There are three things to state when describing an interval. Firstly, major/minor/perfect/diminished/augmented. Secondly a number. Thirdly a direction (up/down). So we can talk about a major third upward such as C upward to E, or a major third downward such as C downward to A♭. This allows us to think mathematically and describe a "diminished unison upward" such as C to C♭, but the interval C to C♭ would be better described as an augmented unison downward.

This is one of many contexts where we do not use negative expressions even though they might make mathematical sense.

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  • Generally speaking, intervals are worked out, thus labelled, from lower to higher notes.
    – Tim
    Commented Feb 9 at 10:31
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    @Tim, not if they are played consecutively. Then the labelling goes from the first note. Agreed if the notes are simultaneous though, in which case there is no need to specify direction.
    – Peter
    Commented Feb 9 at 10:34
  • @Peter Yes, but I would be inclined to not say "augmented first down" and prefer "dimished first" or simply "flatten" when talking about the situation :)
    – yo'
    Commented Feb 9 at 13:47
  • @yo', I would totally avoid using "diminished first", as it gives a negative outcome - the presumed upward interval is actually downward. If C-natural is followed by C-flat it is an augmented first downward. If you play C-natural and C-flat simultaneously it is an augmented first with C-flat as the base note. However I would prefer to call the interval a chromatic semitone.
    – Peter
    Commented Feb 11 at 9:09

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