Music Lesson - Changing the Key of a Composition for Transposing Instruments

One of the most challenging things about composing, whether for an orchestra or a chamber group, is the concept of transposition for instruments who don’t play in the concert key (clarinet, saxophone, etc.) Knowing how to write for the instruments is key for any type of composition. In this guide, we will look at the different kinds of so-called transposed instruments and learn how to transpose for them.

What Are Transposed Instruments?

As you may know, many instruments, such as clarinet and saxophone, read one note and play another, compared to what we call concert pitch (the actual notes as played on a piano). For example, when a trumpet reads a C on paper, the note that sounds is a B♭, a full step (major second) below the written note. These so-called transposing instruments need to have their music transposed to a different key to play in the same concert key as all the other instruments.

For instance, because the trumpet always sounds a major second lower than written, you need to write the trumpet part a major second higher than the pitch you actually want to hear. So if you want the trumpet to play a concert C, you have to write a D; the trumpet reads D, plays C, and everything is right with the world.

The Instrument Groups

Most transposing instruments fall into three groups and are named according to how they relate to C:

• B♭ instruments, such as the trumpet, sound a major second below concert pitch. So if they read a C, they sound a B♭.
• E♭ instruments, such as the alto sax, sound a major sixth below (or a minor third above) concert pitch. So if they read a C, they sound an E♭.
• F instruments, such as the French horn, sound a perfect fifth below concert pitch. So if they read a C, they sound an F.

The following table details which instruments fall into which group:

Transposition Range	Sounds	Instruments
B♭ instruments	Major second lower	Bass clarinet (actually a major ninth lower), Bass saxophone, Clarinet (B♭), Cornet, Flugelhorn, Soprano saxophone, Tenor saxophone (actually a minor ninth lower), Trumpet
E♭ instruments	Major sixth lower	Alto clarinet, Alto saxophone, Baritone saxophone (actually a major thirteenth lower), E♭ clarinet (actually a minor third higher)
F instrument	Perfect fifth lower	English horn, French horn

With a few exceptions, instruments not listed here are nontransposing—that is, what they play sounds exactly as written, in concert pitch. The best example of a nontransposing instrument is the piano; you read middle C, you play middle C, the piano sounds middle C—no transposing necessary.

How to Write for Transposed Instruments

When you write a part for a transposing instrument, you do all the transposing up front by changing the key of the piece for that instrument’s part. That is, you don’t necessarily transpose each and every note individually; the transposition is done by shifting the key signature for the transposing instrument. For example, if a composition is in the concert key of C major, you would write the trumpet part in D major.

A passage in the concert key of C major, transposed to D major for the trumpet part.

Music Notation Programs

Fortunately, today’s music-notation programs automatically perform this transposition for you, saving you the trouble of transposing all the instruments manually. With a program like Finale or Sibelius, you can write the entire piece in concert pitch and then have the program output individual parts in the instruments’ transposed pitch.

Notation programs aside, transposition is still a valuable skill to have. You never know when you’ll need to make changes to individual parts on the fly, requiring real-time transposition. If you can transpose, you’ll also be able to communicate better with individual musicians; when the trumpet player asks you if a given note on his part is supposed to be a D, you’ll know he’s talking about concert C and can respond accordingly.

Now that you know how to change keys for transposing instruments, writing your musical composition will be much easier! Happy composing!

Source from:

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