What variables should I consider when selecting a key?

This is an interesting question, and there have been some interesting answers.

For me, it's pretty simple: what key do I hear the piece in?

I usually come up with an idea in my head (not playing an instrument), and almost invariably whatever key I hear the idea in is what I stick with. Of course, I don't usually hear music for strings in D-flat, nor would I hear a piece for winds in F-sharp minor; my mind is conditioned it seems to avoid inventing music for certain instruments or groups of instruments in keys they don't usually play or sound well in. An exception is choral and piano music, which I am liable to hear in almost any key.

To continue the discussion about strings... I like using a lot of flats, actually. Non-open notes, really. As long as the situation permits, of course. But this is because that certain notes DO project better than others, and if you are playing in the key of ... say F major, your D's, E's (or C's), A's, and G's will tend to sound just a tiny bit brighter. If that is not because they are played on open strings then it is because those open strings will resonate (sometimes harmonics thereof) with those notes mentioned. Much more noticeable in a full orchestra in some passages than a solo instrument, and not very pronounced, but still a small factor. They always tell us to avoid open strings in orchestra... except when we played a "Fiddle" tune, then he said play open strings and harmonics as much as possible. "Be rowdy and make ruckus!" It all depends on what the composer wants, I suppose. The character of the piece, I mean.

Brass instruments should probably be the least of your worries, because we have fewer limits to some extent.

However, a few things should be taken into acount when choosing a key for brass.

Range. You dont want to kill your trumpet player or horn or trombone or tuba players. For trumpet stay underneath a high Bb5 or C6 if you can help it.

Playability. Some trills and runs are going to be harder than others. Especially have to think about lip trills and other effects like that. Flutter tounging can be difficult on some notes (shouldt be a problem with good players), and there are other things. Keep in mind the tone. If your writting below the staff it has a different sound than the middle register and the high register.

Just some thoughts.

Oh and also keep in mind the fact that soem notes are really out of tune mainly C#4 and D4

Originally Posted by theOmaster

This leads me to conclude that woodwinds and brass instruments like flats more than strings for more reasons than just habit. The instruments are made to sound good in those keys.

Another reason is that in sharp keys, clarinets, trumpets and saxophones will end up with a lot of sharps (unless you use clarinets in A). You'll find that most band music is written in a flat key and many arrangements for band have been transposed into a flat key. E.g. Shostakovich's festive overture, which is in A major for orchestra, but for band is in Ab (I think). If it was in A major the Alto and Baritone saxophones would be in F# major and the clarinets and trumpets would be in B which would limit the number of ensembles who could play it. Most professional wind players will be able to play in these keys but don't expect an amateur or youth group to be able to play in them.

But, as J. Lee said, generally it's best just write it in the key you hear it in your head. But be wary of writing fast passages in sharp keys for non-professional wind players.

I'd say, let X and Y be two variables when selecting a piece. How old is the driver?

In my opinion, all keys sound different. For instance, D major is a bright, happy key, whereas A major is even brighter.

Thanks very much for the replies.

Originally Posted by dremits

When I begin to compose a piece, i'm actually not quite sure what key I should choose. I understand that you may need to select a key for reasons such as instrument ranges and ease of play but is their something technical for choosing a key. I mean I compose a lot for piano but I generally choose C major or c minor, just becuase those are keys that are familiar to me.

Thanks

Pick a key, time signature and instruments and see what comes of it.

Originally Posted by note360

Oh and also keep in mind the fact that soem notes are really out of tune mainly C#4 and D4

Anyone who's been playing trumpet more than about 3 weeks amends the third valve slide on those two notes to compensate for the out-of-tuneness do they not? I know I've been taught to do it from as soon as I started really.

Depends where the dart hits.