double-sharp, double-flat questions

[aewanko]

if a double-sharp appears on, let's say, on the F key, does it mean that i'll press G natural?

quite the same on double-flat, if G has a double-flat sign, does it mean that i'll press E natural?

man, these signs confuse me. i want to practice prelude op. 3 no. 2 by Rachmaninoff but the double-sharps make my brain scrambled.

[rhapsody4]

Single sharp = go up one semitone
Single flat = go down one semitone

Double sharp = go up two semitones
Double flat = go down two semitones

So for the examples you gave, Fx = press the G natural key
and Gbb = press the F natural key

Out of interest, how have you managed to get to Rachmaninov's Prelude 3/2 without having learnt that

Good luck.

[keypeg]

Yes, like the previous poster said, double sharps and double flats go up and down two semitones, which is the same as one whole tone.  Most of the time they're the enharmonic equivalent of the next note: G## = A,  D## = E, Abb = G etc.  But since E and F, B and C, are a semitone apart it's better to think of the "two semitone" rule since that's what it is. (E## = F# for example.)

It's less confusing if you know why they exist, so you don't think you have to do anything special music-wise.  THe double sharps and flats are there because of music grammar that composers have to adhere to.  Supposing, for example, that you want to create a minor scale: it has the key signature of the relative major scale. A minor has a key signature of C major.    To create a harmonic minor scale, you also have to raise the note below the tonic by a semitone.  What if that note already has a sharp in the key signature?  Well then, when you raise it a semitone, it will have two sharps, and voila - double sharp.  The key of G# minor, for example, has the key signature of E major, with four sharps.  The note below the tonic, G#, is F# in the key signature, so it's already sharped - but it has to be sharped again to raise it a semi-tone.  So the composer has to add a second sharp to an F##.  Effectively you're playing G but you are reading F##. 

Why can't the composer simply write G, then?  Because then you would have two note names in one scale, and that's against the rules.  If you didn't use F##, then your last three notes in a G minor scale would be E G G# ... two G's.  But this way you have E F## G#, and the sequence of notes remains intact.  Apparently they call all of this musical "grammar".

[guendola]

if a double-sharp appears on, let's say, on the F key, does it mean that i'll press G natural?

quite the same on double-flat, if G has a double-flat sign, does it mean that i'll press E natural?

man, these signs confuse me. i want to practice prelude op. 3 no. 2 by Rachmaninoff but the double-sharps make my brain scrambled.

Absolutely correct. But do yourself a favor and think Fx instead of G, because the scale always has 7 notes and there is always an E and an altered G arond the Fx (in the scale). If this doesn't make sense to you now, just do it. You will understand later, it will eventually click in your head.

PS: Whoops! Double flat G is played on the F-key, not on the E-key, so your initial post was a bit wrong after all

[keypeg]

quite the same on double-flat, if G has a double-flat sign, does it mean that i'll press E natural?

Just saw this: No, you play F natural.  Think of the accidentals as traffic signs that you follow blindly.  One flat means "go down a semitone".  Another flat means "go down another semitone".  So you see Gbb, you go down a semitone from G for the first flat, and you're on the black key below G = Gb; then you go down a semitone from there to the next semitone, and voila, you're on F.

Are you studying theory?  That would help a lot.

[mike_lang]

Or perhaps, one might think of it this way, which for me is easier than perceiving double alteration:

In the key of C-sharp Major, the sharped fourth scale degree is (F-sharp)#.  It is not G, but simply a semitone up from F-sharp.

In the key of C-flat Major, the flatted seventh scale degree is (B-flat)b.  Same explanation as above.

[aewanko]

wow. all good advice

Single sharp = go up one semitone
Single flat = go down one semitone

Double sharp = go up two semitones
Double flat = go down two semitones

So for the examples you gave, Fx = press the G natural key
and Gbb = press the F natural key

Out of interest, how have you managed to get to Rachmaninov's Prelude 3/2 without having learnt that

Good luck.

the power of guessing, my friend. i'm actually just starting.