I have a pupil who is working through the "Grade 4" theory book. (!) I have explained that - B to F# is a "Perfect 5th" - and B to F nat. is a "dim. 5th" - The tedious 15 year old then asked me "what is B to f flat?" (!) I have posted this on the "Sibelius" message board - and have been told "double dim." (!) I don't think this is correct (?) (Obviously a 5th of SOME discription !)

Your advice would be appreciated.

All the best.


Russell

The interval from B to F flat is "Doubly Diminished 5th". You may want to verify this in AB's Theory Book (Bk I) by Eric Taylor.

Would it not be the case that since F flat does not occur in either B major or B minor, you would then have to "spell" the B as a C flat. In which case the interval then becomes a simple perfect fourth from C flat to F flat. It's all to do with spelling.

you can't just re-spell a note to make the answer easier

A double diminished chord does not naturally occur in music - surely an F flat would ALWAYS be spelled as an E in a B major/minor piece. Can you find a piece of music (that is not bi-tonal) where the key is B major/minor with an F flat in it?

No, probably not.... but that was not the question.
The original question was more like 'what if....?'

Intervals differ by a) the number of scale's steps inside, the number of whole tones (halftones) inside; a) determines the names of intervals as "second', third', or 'fifth'; determines the size of interval, e.g. whether this second/fifth is great or small/perfect, diminished or augmented.
The enharmonic 'renaming' of given sound (fron B to C flat) changes the name of interval (fourth instead of fifth), not the actual 'size' (2 and a half tones). If you (or composer) shoose to hame given compbination of sound as B - F flat , it will be double-diminished fifth; if C Flat - F flat - perfect fourth. This choise is dictated by the tonal background of given sounds' combination; if you are in A Flat Major, the interval in question MUST be notated as B natural (IV+) and F flat (VI-); there is no place in A flat MAJOR for C flat! Therefore, you are dealing with double-diminished fifth as the part of the chord of altered subdominant (second seventhschord with root+, 3+, 5-).
Bytheway, this chord, and, therefore double-diminished fifth are VERY NATURAL for classical music. Check, for example, such a pop hit as slow movement from Beethoven's Fifth Symphony: d-diminished fifth helped the enharmonic modulation from C Major into A flat Major (because, d-diminished fifth is enharmonically equal to perfet fourth). Anothr example: enharminc modulation in the middle section of Chopin's Notturno C# Minor

Best regards

And people wonder why I hate intervals??

I almost understood that!

"I almost understood that! "

You mean explanation or spelling mistakes?

Best regards

B to Fb is B to E, therefore it's a fourth! Does this really have to be so complicated???

B to Fb is B to E, which is a fourth. Does this really have to be so complicated?

No wonder some people " hate intervals" if they have to be made so ridiculously complicated. Sheeesh!!!

Violinia

QUOTE (Violinia @ Jun 29 2004, 09:06 AM)

No wonder some people " hate intervals" if they have to be made so ridiculously complicated. Sheeesh!!!

Now you all see why we do hate them!

But please don't hate all intervals! The only thing to have a problem with is the over-complication of intervals by defining them in an over- complicated context, like calling something a "double-diminished" when in itself it is just a fourth, plain and simple.

Sometimes I think music theory can go to a place that's quite beyond the pale.

Violinia

I agree with Violinia - WE RULE!!!!!!!!

QUOTE (asagohan @ Nov 16 2003, 04:54 AM)

The interval from B to F flat is "Doubly Diminished 5th".

Would B double sharp to F double flat be a quintuply (sp?) diminished 5th?!

Of course, there's the question of what's the interval between B and F double-flat.
You have to B# to C that...