How to Transpose Music for Your Instrument
What Is a Transposing Instrument?
It is a musical instrument whose notes are written in a different key from the pitches that sound when it plays. For example, a B flat Clarinet, or French Horn in F. When the concert key is C, a B flat clarinet will sound a B flat when it sees the note C. When a french horn sees the note C, it sill sound an F below C.
Why are there transposing instruments?
Many instruments differ in size. The flute, clarinet and saxophone are all very different sizes. They all have different ranges (different highest and lowest notes) and the larger the instrument, the lower the notes it can produce. Most instruments in the woodwind family, for example, use the same fingering so that a woodwind player can play several instruments, based on using the same fingering patterns. As a result, instruments are transposed based on their range, and that the fingering is identical.
Concert Key and Instrument Key
Instruments that transpose are said to be in a certain "key." Examples would include, B flat clarinet, horn in F (french horn) B flat trumpet, etc. The key the instrument is in indicates which pitch will sound when the player plays C. Clarinets in B flat that read a C will sound a B flat below C. A french horn player that reads C will sound an F below C.
Transposing for Your Instrument
So if an instrument will sound notes lower than C, then you would have to write the pitch higher than C to get the right pitch. Clarinets in B flat will sound a whole step lower than the pitch it sees on paper. So to get it in the right key, you have to write the part a whole step higher to sound a C. That means you would have to write a D in order for the clarinet to sound C. So when concert key is C, your key signature is D. If you are in the concert key of G, then your clarinet part needs to be in the key of A, and so forth.
For French Horn, which is in F, a middle C will sound a perfect 5th below the written pitch (sounding F below middle C). Therefore, to sound a C, you need to write the key signature a 5th higher than concert key. So for horns in F, if the concert key is C, then horns in F are in the key of G.
So whatever the concert key is, you compensate by going the opposite direction at whatever interval the instrument is away from C. So an E flat instrument usually sounds a 6th lower than middle C, on a low E flat. So you would have to write it a 6th higher than C to be in the right key (A flat).
Remember the basic rule is that whatever interval lower or higher the instrument sounds from written C, you transpose in the opposite direction to get the right pitch to sound. If the instrument sounds lower than C, then you transpose by going the same distance higher than middle C.
Other Resources and Helps
Other related articles about music and music publishing include: "Learn to Read Music in Ten Minutes," here, "DIY: Publish Your Own Sheet Music," here, "Do I Have Perfecct (Absolute) or Relative Pitch?", here, "How to Find a Sheet Music Publisher," here, "How to Play Piano with Nine and One Half Fingers," (humor), here, and "A Piano Parable for Christmas," here.
Here is complete list of articles and topics by Daniel Carter.