Why are brass instruments more comfortable with flat keys?

Question

Taken from the first answer to this question: Should you write in F# Major or Gb Major?

Some instruments—like brass—are more comfortable in flat keys. Although players should be able to play in all keys, your brass players will make fewer mistakes in G♭ major, trust me :-)

why is this?

I can understand why some keys are more practical for some string instruments, but I am completely clueless when it comes to brass (experience: trying to make sounds with a corroded trumped for 5 min when I was 11yo)

Answer 1

First of all, many brass instruments are transposing instruments in a way that adds sharps. The most commonly used trumpet is in B♭, horn is in F, and even though the low brass read at concert pitch, trombones and euphoniums are based in B♭ and tubas can come in F, B♭, or E♭ (as well as C). That is, for the purpose of this discussion, trombone, euphonium and the low tuba are effectively B♭ instruments. So the instruments are naturally centered more around B♭ than C.

When we transpose a trumpet, its Cs and Gs are always fingered open (no valves pressed). In a technical passage, having open fingerings mixed into the line makes things easier. As we deviate from C major and add sharps or flats, C and G are among the last pitches to be flattened, but among the first to be sharpened. And remember that for a B♭ trumpet we're starting with two sharps. So a piece in concert G results in the B♭ instruments playing in A, and there are significantly fewer open notes (upper Es are also open). This isn't a huge challenge and I always say that fingerings are not the hard part of playing brass instruments, but it is something.

There are also some tuning issues. The low written C# / concert B is a particularly ugly note, which obviously shows up much more often in sharp keys. And there are some other more minor tuning issues that tend to be more easily dealt with in flat keys, but I'd have to get deep into the physics to really explain why.

Answer 2

From what I've noticed is that (often) flat keys are not harder to play but can be harder to read. (Similarly for clarinets and saxophones.) A piece in concert C is written in D for Bb instruments (not too bad.) A piece written in concert E will be in F# for Bb instruments and C# for Eb instruments. There are pieces in B major (sometimes in B minor then moving to B major) which calls for C# major. Most people find keys with a larger number of sharps (or flats) harder to read (not really harder to play) than those with fewer.

Answer 3

I think all comes from the origin of the F scale which is very easy for the fingers 1,0,12,1,0,1,0,1. *)

And March compositions are modulating a fourth up in the Trio-Section. So we always are going though the circle of fourths.

(Actually Brass pieces have rarely more than 4 or 5 sharps or flats.)

*) For beginners the use and change 23-12 in E-major is a bigger challenge.

Edit: Another point!

Mind that Eb-Horns have one sharp more than Bb instruments.

Edit:

Yes, I’m talking about brass band music that might be written for amateurs and beginners. And I supposed the question is referring to these. Profis won’t have problems to play in sharp keys anyway.

But in the pop/rock scene we have another problem, also for amateurs and beginners:

When I was arranging songs for school bands the key E-major was quite easy for guitarists But this meant for Bb brass instruments F# or Gb. Now as we know this music usually extends by secondary dominants in sharp key regions what would complicate the reading again for Bb instruments: e.g. A#7-D#7-G#7-C#7->F#. The accompaniment or the soloist parts will be Bb7-Eb7-Ab7-Db7->Gb and obviously much easier for reading in Gb than ib F#.