http://en.wikipedia.org/wiki/Theoretical_key

What sort of theory grade does the information given on the link above about such keys as Gb minor, Bbb major and Cb minor get included in?

I'd be interested to know if that is grade 6, 7 or 8 theory (or higher if there is a higher level), because it's certainly not in the grade 5 theory papers that I've done.

Unless I missed something they don't feature at all.

That's a relief!
They seem like an awful lot of complication for no real reason.

Forget it - there is no need to go beyond the conventional key signatures of up to 7 sharps or flats in any AB theory exam, including grade 8. Must admit, I'd never even heard of this stuff. Don't think it has held me back...

And you a proper composer an' all - tut tut......

That Wikipedia article is pretty bad tbh. Doesn't make much sense.

And no, none of that is on the syllabus for any of the theory grade exams.

Occasionally having some knowledge of this might be helpful ... I was struggling with a passage in the 1st trumpet part in 42nd Street (double sharps etc.) until I realised that the A# was the tonic for the eight bars. Once I'd realised it was just Bb major written in a silly key, all was fine - my fingers knew what to do.

I remember having a very strange dream that I was trying to figure out how many flats there were in Fbb major (15). I think I must have been studying music for too long.

A couple of times in my oboe lesson my teacher has asked me to play "Si bémol" major or minor scale. I hear it as "C flat" and dutifully work out that he really wants is B. It's only when I'm half-way through the scale and he asks me what I'm playing that I realise what I have done.

The really stupid thing is that each time I wonder why, if he wants B, he doesn't just ask for B instead of trying to confuse me by asking for Cb. Never once have I thought, hang on a minute, maybe I've mistranslated .

Maybe he wants to make you aware that the so-called theory of music is not a proper theory at all but rather a conglomeration of rules, conventions and weird names for everything, which gives us plenty of material for examinations.

Ina

Sometimes I touch on theoretical keys when I'm trying to work out intervals from weird notes... there must be an easier way to do it, but I haven't found it yet.

Without being able to quote a reference, I get the impression that keys that need double sharps or double flats are not taught in the UK. I suspect they may be in France. Poulenc piano parts occasionally modulate a very long way so that you must expect to find the occasional large chord with an accidental on every note.

A curious aspect of our notational system is that by using triple and higher accidentals you can make it open ended in both directions, when for practical purposes the keys available with the five inflections are already more than you need. When you map notation onto the fixed pitches of the most popular equal tempered tuning systems, ET12, ET19 and ET31, you close it cyclically in a arbitrary way.* ET53 introduces a problem, however, because it distinguishes major and minor tones, so that, e.g., you have two choices for the pitch of the major sixth: the third above the subdominant is flatter than the fifth above the supertonic.

* Each has its own set of enharmonic equivalents.

There is.
Change both notes by the same amount until you get a more 'sensible' starting point.

thanks sbhoa, I will make a note of that