Bb versus Eb (transposing instruments)

Why are some brass instruments said to be “in Bb (B flat)”, or “in Eb (E flat)”, or “in F”, or “in C” (also known as “Concert pitch”) or other musical notes?

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For example, the standard Cornet is a Bb instrument, whereas the Soprano Cornet is in Eb; the Tenor Horn is an Eb instrument, whereas the Baritone Horn is in Bb.

The Trombone is a Bb instrument when playing music in the Treble Clef, whereas it is in C when playing music in the Bass Clef or Tenor Clef.

Tubas come in two sizes: Bb and Eb; French Horns come in two sizes: Bb and F and these are usually combined into one Bb/F instrument; and Trumpets can be Bb or C, or even A, D, Eb, E, F or G!

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Well, it depends on what note the instrument produces when the player plays a “C” on the music score.

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Now, at this point you are probably thinking “but the answer is obvious and trivial – if they play a C then the note produced is … C surely … isn’t it?”.
Ha ha! If only it were that simple, you poor foolish people (evil laugh)…

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A standard Cornet player plays a C with no valves pressed down (“open”) but the note produced is actually a Bb as played on a piano.
The note C played on a Soprano Cornet is actually an Eb as played on a piano.
The note C played on a Trombone when reading Treble Clef is a Bb as played on a piano, but when reading Bass Clef it really is a C as played on a piano.

Notes played on a piano are said to be at “Concert pitch”. Concert pitch itself can vary, and has varied over time, but nowadays is generally set to an International Standard pitch in which the note A above middle C (the A between the second and third lines of the Treble Clef music stave) has a frequency of 440 vibrations a second (440 Hertz). Wow, can your lips really vibrate that fast? 440 times a second? Amazing! No wonder they get tired!

If the notes played on an instrument sound the same as they are written, then the instrument is said to be “in C” or a “Concert” instrument.

Any other instrument, where the notes sound different from how they are written, is said to be a “transposing” instrument, and it is “in” the sounding note played from a written C.

Brass instruments are usually “Concert”, or “in C”, when playing music in Bass Clef, and usually “transposing”, e.g. “in Bb” or “in Eb”, when playing music in Treble Clef.

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Now, where were we? Oh yes, a standard Cornet, most Trumpets, and many other other brass instruments, are “Bb” (B flat) instruments because when they play the note C as written, they are actually playing a Bb.

and a Soprano Cornet, a Tenor Horn, and some other brass instruments, are “Eb” (E flat) instruments because when they play the note C they are actually playing an Eb.

Right, ok, so now we know …. I think? I might need to go over that a couple more times …

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Why would you do that? Why is it so …complicated? Why can’t everyone just play a C and actually play … a C?
Wouldn’t that make more sense? Surely that would be easier?
Aha! You’d think so wouldn’t you? Yeah, but…
… there is a very good reason for it: a brass player who reads music can more easily switch between playing different brass instruments.
When they see the note C written down, they know to play a note with no valves pressed down, whatever the instrument (the trombone is different of course). It’s up to the person writing the music to make sure the right sound comes out. So if I play a Bb on a piano and I want my brass players to play the same note, I’ll ask the standard (Bb) Cornet to play a C and the Soprano (Eb) Cornet to play a G. Written down, it looks like they are playing different notes, but when you hear them, the notes sound the same!
So now, the brass player can happily practice and practice until they can read music, press the right valves and play the notes as easily as you can read a book and say the words without thinking too hard, if at all, about the spelling and how to say each word.
E.g. a Cornet player can switch to playing Tenor Horn or vice versa. They will have to adjust to a different sized mouthpiece and the range of notes they can play, but they don’t need to worry about which valves to press when reading music!
Now, isn’t that a great result? Woo-hoo!

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