Hi,

Basically my question(s) is: if I have a composition/improvisation in mind, which key should I select to work in ? And why ?

Some more background.
I am practicing the piano now for about 5 years, in which I learned both playing the piano (modest level of course) as well as (basic) music theory. This last includes intervals, chords, progressions, circle of fifths, harmony etc etc. In the course of last year, I started with composition/improvisation of small, simple things to apply all this technique and theory also to (my) practice.

However, there is still one question I could find no satisfactory answer on: which key should I use ? And why ?

You can turn this question into multiple other, similar/related questions.
Why is a piece written in a certain key (and not in another one) ?
Why is not everything written in C major/minor ?
Why should I prefer G over F ? On what basis ?
...

While I can more or less understand for written pieces I study, in that otherwise too many # or b's would be required eg, I have a more fundamental question: why do they use these # and b's in the first place ?
So, when I have a composition/improvisation in mind, maybe only conceptual, how do I decide which key would be best ? Why are the Goldberg variants of Bach in G major ? Rather, why did he choose for G major in the first place ?

Sorry if this question has already been answered in one of these forums, but a search did not yield a direct related topic.

Thanks

Mmm...

That's a very tough, and very subjective question. For me, once you start playing with sounds for a bit, you'll have a "natural" perception of what key to use once you get some experience and once you listen to a lot of repertoire and do some score studying. It's hard to actually create a logical system of "this key = this emotion = this quality," etc. (Plus, when you're dealing with Romanticism and later, you have a trend toward the lack of key, or the multiple switching of keys - especially with atonality, the use of a key signature is subjective.)

Someone might have a more straightforward answer, but those are my two cents.

Let's see. Here are some reasons.

1) If you are composing for a singer, you have to adapt the general sound of the song to the range of notes the singer can do. If your singer can sing perfectly from G3 to A4 (for example), I would write the song in G Major key, because the sounds on the scale are between that notes. If I choose B or C, there are notes out of the range of your singer: if you want to use from C3 to C4, he can't sing the notes from C3 to G3. And if you choose C4 to C5, he won't be able to sing notes from A4 to C5.

2) You have to think also in the instrument you're using. For example, the easiest key in viola is D major. Why? Because of the hands position. In wind instrument you can have the same problem: there are keys wich are more difficult than other.

3) Your facility to compose with that key. Your preferences are important also. Try to make two compositions about the same theme. You will think in a different way and one will express something a little bit different from the other. In my case, if I want to make something sweet, I choose flats or E Major key. Why not A Major? It's difficult for me in that key. See what keys you like and compose in that.

4) The sound. If you're doing something for piano, for example, and you have big chords in the left hand, you shouldn't have it very low. (For example with the root on the C1) How do you solve this problem? Changing the key. Instead of C, use B key. Noiw, the root is not C0, is B0, you've transposed it a 7th up. With that, you can avoid dark sounds, for example.

I hope you understand my explanation. That are my reason, maybe somebody has more ^^

Thanks for your answer !
Explains why also my teacher did not give/could not give a clear answer... :-)

On the atonality etc, I agree, that's yet another matter: I once asked my teacher in which key a piece of Debussy was in... Wrong question apparently :-)

Ok, thanks for these reasons (Victor Seven).
Now, I am playing the piano, not writing for singers (at least not now), so 1 and 2 are not really applicable in my case according to me.
Point 3 however is a good tip I think: probably the best way to figure out is working in the different keys indeed. Fun !
Point 4: understood.