Am I right in saying that the seventh chord in C (when harmonised) is Bbm7b5 - notes are Bb,D,F,A? So then also am I right in saying that a Bbdim7 contains the notes Bb,D,F,Ab.....I just want to confirm the difference between the two different chords. Thanks in advance.

I think that you're talking about Bm7b5(= B half diminished 7th) and Bdim7, NOT Bbm7b5 & Bdim7 . . .

Bm7b5 = B D F A

Bdim7 = B D F Ab



Note that Bb, D, F and Ab is Bb7 (dominant 7th chord built on Bb) and that Bb, D, F and A is BbM7 (Major 7th chord built from that same Bb)


Hope that helps you out some.

Bbdim7 = Bb Db Fb Abb

I think that you're talking about Bm7b5(= B half diminished 7th) and Bdim7, NOT Bbm7b5 & Bdim7 . . .

Bm7b5 = B D F A

Bdim7 = B D F Ab

Note that Bb, D, F and Ab is Bb7 (dominant 7th chord built on Bb) and that Bb, D, F and A is BbM7 (Major 7th chord built from that same Bb)

Hope that helps you out some.

But isn't this a good example of how the chord symbol system sort of breaks down?

A 'Bdim' chord (with no 7th) would use B D F.
A 'Bm(b5) chord (with no 7th) would use B D F.

So then, what is the difference? When we add the 7th (a minor 7th) to this chord generally we'll call it a Bm7(b5). If we want the fully diminished 7th we'll call it Bdim7, but the basic chord is the same, so the use of the 'm(b5)' or the 'dim' is really having an impact on the spelling of the 7th, and not the 5th. And that is confusing.

Of course an answer is to use the little circle for fully diminished 'Bdim7' and the circle with a slash for 'Bm(b5)7'.

Generally speaking Chuck, the chord symbols refer to 4 note chords. Bdim implies a dim7 chord. You'd have to specify a triad if you only wanted that sound.

Oh yea, I agree totally. It would seem that most diminished or half diminished chords have a 7th. And too, most players will assume a 7th on a minor chord. A lot of Piano players will put 6th's and 9th's on a major chords (and occasionally a non requested major 7th).

Chord symbols seem to live in a murky world between theory and practice. I was just pointing out that two different ways of writing a diminished triad have no effect on the triad, but rather have an affect on the 7th.

Mark Levine does a fairly good job of spelling out these hassles in the intro to his book. But he doesn't even get into diminished chords or flat 5's as such. And while he is very clear on what to expect in the book, there are several symbols that are very different from what I was taught years ago.

Sorry guys my mistake for putting Bb....I meant B. So although the 7th chord of C is a Bdim...you would actually play a Bm7b5 as opposed to a Bdim7 to resolve the harmonised C major scale because the Ab in the Bdim7 isn't harmonically correct as it shold be an A. Apologies for making this sound more confusing than it probably is but I just want to clarify. Thanks

But isn't this a good example of how the chord symbol system sort of breaks down?

Nope, triads is triads. There's no difference between the "triad" part of a dominant chord or a major 7th chord, right? You can't talk about triads and chords with tensions as if they are the same thing.
It's like you're saying "Doesn't the whole fruit thing break down because an orange isn't an apple?"

[QUOTE=Ed Fuqua]There's no difference between the "triad" part of a dominant chord or a major 7th chord, right?QUOTE]

Right. A C7 chord (C E G Bb) has the same basic triad (C E G) as a Cmaj7 (C E G B). The difference is the 7th of course and the sound is unmistakably different. (even though the basic triad is the same). But the chord symbol difference is in reference to the 7th.

In the previous posting I was only making the point that in the case of a Bdim7 the basic triad (B D F) is the same as a Bm7(b5). In this case the difference in the chord symbol has a reference to the 5th yet the basic triad remains the same in both cases. Its the 7th thats different, yet there is no notation that refers to the 7th.

Another way to state this. If we were together at a piano and I played the notes B D F and asked what the chord would be called one would probably answer, "B diminished". If I then added an A natural would the previous answer have to be changed to B minor flat 5?

Another way to state this. If we were together at a piano and I played the notes B D F and asked what the chord would be called one would probably answer, "B diminished". If I then added an A natural would the previous answer have to be changed to B minor flat 5?

No, the previous answer wouldn't be changed at all. The *current* chord is Bm7b5, the previous one was Bdim.

I see your point, but I don't really think it's a major issue. The system isn't breaking down if everybody still knows what's meant.

What's the problem with understanding the "dim" in "dim7" as applying to the 7? Isn't that what we do with "maj7"? "Dim" is the correct term for a double-flatted 7, as you know.

I think the way to look at it may be this: the "dim" applies to the 7--i.e., "dim7" is a unit like "maj7"--and the presence of a diminished 7 *presupposes* that the basic triad is a diminished one unless otherwise specified. We do the same thing with other 7 chords. When you see "maj7", you presuppose an underlying major triad unless otherwise specified. Same with "7". When you see a 7, you presuppose a major triad underlying it unless otherwise specified (i.e., as augmented, minor, or minor flat 5).

I gues part of the issue is that some of the same terms are used to describe the nature of a single interval as are used to describe the character of a triad, as Ed suggested. But that's just how it is, and it's not illogical IMO.

Sorry guys my mistake for putting Bb....I meant B. So although the 7th chord of C is a Bdim...you would actually play a Bm7b5 as opposed to a Bdim7 to resolve the harmonised C major scale because the Ab in the Bdim7 isn't harmonically correct as it shold be an A. Apologies for making this sound more confusing than it probably is but I just want to clarify. Thanks


Yep, the Bm7(b5) (half dimished 7th chord) (BDFA) usues notes that are in the key of C.

Another way to state this. If we were together at a piano and I played the notes B D F and asked what the chord would be called one would probably answer, "B diminished". If I then added an A natural would the previous answer have to be changed to B minor flat 5?

No, the correct answer would be B diminished triad. and if you add the seventh THEN the chord becomes a ahlf diminshed chord. But it doesn't affect your prior answer, B D F is STILL a dimsinshed triad.

If I play a B D# and F#, that's a major triad, right? If I then add an A, it doesn't suddenly become a "dominant" triad.

You're still trying to analyze apples in orange terms...

Oh I know it's no big issue at all. Frankly I just enjoy thinking about it and discussing anything with music. The system isn't breaking down.... its a shortcut with all its good stuff and bad.

I was taken by the Mark Levine book that I got a few weeks ago, just how 'complex' some of the chords look. And it just that there are some really good examples of music being made today that are very close to atonal and/or bitonal. In those cases the chords symbols really begin to take on a complex look.

When I was a kid no one would have used the symbol C2. And the first time I saw that I had to take a step back. But clearly its what would have been called a 9th chord, but without a 7th (which would have been included- who really wants to read C9(no7)). Things like C4 also looked a little strange, but that is a clearer symbol that Csus (just what is suspended over the C anyway?).

Anyway, I know the next time I write a chart and use Bdim7 I'm going to hear an "A" in that chord until I say something. And probably more likely if I write a Dm I'll hear a C along with it. If there is a Bb chord you can almost count on hearing a G and maybe a C also. Last rehearsal there was an argument with the keyboardist and the guitar, one was calling a chord a Am7 the other a C6. (the bass player is the referee in that case).

Whadda gonna do, its just music.

Bdim7 = B C# D E F G Ab (A#) ; Ab = dbl flat 7. Dim chord contains two dim intervals, 5 & 7.

Bm7b5 = B C D E F G A : aka Locrian or half dim.

Bdim7 = B C# D E F G Ab (A#) ; Ab = dbl flat 7. Dim chord contains two dim intervals, 5 & 7.

Bm7b5 = B C D E F G A : aka Locrian or half dim.

Of course, you don't *have* to play those sets of notes with those chords. :)

Of course, you don't *have* to play those sets of notes with those chords. :)
Nope. Nosiree. Ya sure don't.