# What does the '°' notation signify?

I just saw this comment by Tim, in another question:

`D°` can't have a C. It's spelt D, F, Ab, Cb.Or as a triad, just the 1st 3 notes. Ao/F is F b9, and Ao/F# will just be F#o. Or D b9/F#. If this helps - hope so.

What exactly are `D°`, `A°/F`, `A°/F#` and `F#°`? This is the first time I have seen something like this.

• I assumed that was just a diminished sign in an easier to type form. Technically it should be a superscript degree sign, but that's not easy to input in Stack Exchange. – Pat Muchmore Jan 27 '15 at 15:29
• I've edited your Do by `D°`, that means `D°` isn't Do. `D°` = D dim and `D°7 = D dim 7. Also Ao and F#o are written wrong. – Albrecht Hügli Jun 4 at 12:35

The 'o' bit designates dim, or diminished. Slightly different from the ø which is half-diminished.(Which was pointed out by someone as wrong - it should be a third diminished!) Wish my keyboard could print it properly - it probably can, but I'm not clever enough to make it work! Half-dim.,(that could even be me...) incidentally is aka m7b5.

• I'd just like to point out that perhaps the oldest known half diminished seventh chord, in this case b d f a, comes in the English medieval canon Sumer is icomen in. – Scott Wallace May 30 '17 at 15:10
• @ScottWallace - I'm betting it's actually V9 without the root. Can't say I know it. Must listen... – Tim May 30 '17 at 15:15
• @Tim- yes, do listen to it. But the way the piece is constructed, basically alternate I and ii chords in Ionian, makes the V9 a modern interpolation. – Scott Wallace May 30 '17 at 15:19
• @ScottWallace - can't find the run mentioned in any of the dots I've trawled through. – Tim May 30 '17 at 15:27
• @Tim- I guess everything is off subject, if you just look at it hard enough. Yes, with modern ears, it sounds like a g-b-d-f-a ninth chord, minus the root. But the g never happens in the whole piece as root of a chord: this is a good example of an ionian piece that is decidedly not major. – Scott Wallace May 30 '17 at 16:20

`What does the '°' notation signify?

`°` means `diminished`, which means that you play a minor chord with a flattened five.

`What does the 'X/Y' notation signify?

This is called `slash chords`. This means that you play an inversion of the `X` chord where the lowest note is `Y`. Example: `C/G` is played as `G`, `C`, `E`.

In some cases, like the ones that you present, an extra note might be added that is not necessarily a part of the original chord. Example: `C/Bb` is played as `Bb`, `C`, `E`, `G`, which is just an inversion of `C7` with the seventh note in the bass.

What is `D°`?

`D`, `F`, `Ab`

What is `A°/F`?

`F`, `A`, `C`, `Eb`

What is `A°/F#`?

`F#`, `A`, `C`, `Eb`

What is `F#°`?

`F#`, `A`, `C`

I found this site to useful: https://www.pianochord.org/

To find out what `D°` means, then you

• select `D` in the top bar
• check through the `D chord categories`; since it's not there, you
• go down to the `Explanations` below
• find `Ddim - D diminished (D°)`
• select `Ddim` in the listing above

This gives https://www.pianochord.org/d-dim.html

On the website, you also get help to fingering.

• I wonder why in this collection of chords there is no D dim7? D°7? – Albrecht Hügli Jan 24 '19 at 11:59
• I don't know whether it has been added in the meantime. But it's there now. – Little Helper Jun 4 at 10:25
• "which means that you play a minor chord with a flattened five" While that's true, to me,a dim is different from a m7b5. Both are a minor chord with a flat 5, but the 7th of the former is 1/2 step lower than the latter. – Duston Jun 4 at 13:12
• @Duston, I completely agree that `dim` and `m7b5` are different, but notice that I'm talking about `dim` and not `dim7`. I also agree with you that `dim7` and `m7b5` are different by the 7th being shifted a semitone. – Little Helper Jun 4 at 13:51