When is a C not a C? It’s not a riddle or a trick question. It’s

a musical principle. The answer is: a C is not a C when you’re

playing a transposing musical instrument. And it’s not the instrument

that transposes, unfortunatly — some arranger or the player

himself must do that.

To understand what this means, you first have to understand the

definition of concert pitch. Pitch, of course, refers to the

frequency of sound. Concert pitch is the universally agreed upon

definition of the pitch of middle C (and subsequently, every

other note in an octave). From the dawn of written music to the

present day, no matter where on earth you are, middle C always

sounds the same. In other words, every musician in the world

understands and interprets middle C in the same way. This is the

simple definition of concert pitch.

Many instruments, therefore, are manufactured to concert pitch.

This means that when multiple musicians read “C” (or any other

note on a scale) on a musical score, they produce identical

sounds. Instruments that are manufactured in concert pitch

include the piano, some brass instrumnets such as the trombone

and baritone, some woodwinds such as the flute, oboe, and

bassoon.

Many other instruments are not made to produce concert pitch

sounds. These are referred to as transposing instruments. Many

woodwind instruments and some brass fall into this category. When

a transposing instrument player reads and plays “C” in a musical

score, it sounds different from a “C” played by a non-transposing

instrument.

Therefore, music that is written for a band consisting of both

transposing and non-transposing instruments must be adapted for

individual types of instruments. A typical marching band, for

example, may have the same score of music transposed into two,

three or more different keys.

The clarinet is an excellent example of this. It is a transposing

instrument, typically manufactured in B flat. If a B flat

clarinet and a piano played a “C” at the same time, the sounds

produced would not be the same. In order for a B flat clarinet to

play a note that matches a piano playing a “C,” it would have to

play one whole step higher. In other words, it would have to play

a “D.”

What if the two instruments had to play a song together? Music

for the piano would be written at concert pitch. The same music

would have to be transposed one key higher so that the clarinet

would produce the same sound. Though the two songs appear to be

in different keys, the sounds that each instrument would produce

will match in pitch.

Bb instruments include the Bb clarinet, the Bb bass clarinet, the

Bb tenor sax, the Bb trumpet. Music for these instruments are

written in a key which is a whole step higher than concert pitch.

Eb instruments include the Eb clarinet, the Eb alto clarinet, the

Eb alto sax, the Eb bariton sax, and the Eb alto horn. Music for

this group of instruments needs to be written a minor 3rd lower

than concert pitch.

F instruments include the french horn and the English horn. Music

for these instruments must be written in a key that is a perfect

4th lower than concert pitch.

It sounds complicated. You may even ask: why not just manufacture

the clarinet (or other transposing instruments) in concert pitch?

Though it seems this would solve some problems, there are good

reasons that certain instruments produce other pitches. The B

flat clarinet is preferred because it produces a cleaner, more

pleasant sound than a C soprano (concert pitch) clarinet. In

fact, the same is true of many transposing instruments. So while

using transposing instruments make more work for the composer, in

the end it’s all about the product. Serious musicians are known

for their keen sense of hearing. Since only the best quality

sound will do for them, composers will keep writing scores with

both types of instruments in mind.