Dear all,

My student has thrown me a question which I am unable to answer...

I was hoping that you guys could offer me some light...

Question :

An F to a C, would be a Perfect 5th interval.
an F to a C#, would be an Augmented 5th interval.
What then, is the interval name, for an F to C## (double sharp)??

To be honest, I've no clue...I've never come across questions like that...

Thanks for your help!!

I hope someone will correct me if I'm wrong, but I believe it would be called a double augmented fifth.

Steven

Yes, it would be called a double augmented, although you don't really run into that very often. More is explained on wikipedia, which I cannot post here because the url has parentheses in it, and so, do a search for double augmented intervals and you'll find it.

I'm glad I've never been asked that...I would have been bummed too.

Well, now I know.

Isn't it great when you get a question you can't answer?

I usually say, "See if you can find the answer to that yourself before next lesson".

Then I sign on to PW for help.

I would call it a doubly augmented 5th.

the trick is to remember that in formal analysis, the letters determine the interval, so you have to go with it, no matter how ridiculous it seems.

I'd want to see a very good reason for writing such an interval, but strange situations arise in which almost anything that seems ridiculous may be needed.

It could be worse.

Fb to Dx would be triply augmented. I can't think of any situation in which it would be used, but there you go!

Here\'s the Wiki explanation , Morodiene was referring to.

O/T:
For future reference, you can use this site to correct those irritating hyphen problems with the URLs at Wiki.

When would it occur in music, or would it occur, I wonder?

Here is the type of situation when that is most likely to occur.

B E G
*B Eb G
B D G

but

B D G
*B D# G
B E G

This interval is not rare at all in chords. In fact, it's necessary to show chromatic movement. So on this point Wiki is extremely misleading. All augmented chords whose middle note is a "black note" will have two spellings, and either will have a slight problem. For instance, B D# G contains a diminished 4th.

They are most likely to occur, again, in chromatic movement:

F Bb
*Fb B (natural), doubly-augmented 4th
Eb C

The theoretical advantage to such a case is that if you are in a key signature with two or more flats, you save one extra sign. Instead of having to notate E natural and the follow it with a flat after the E, the only accidental would be the flat after the F.

As odd as such intervals might seem at first glance, they appear much more often in the music of composers whose writing contains a great deal of chromatic movement.