TL;DR: The clarinet is “in B♭” because when you play a written C, the pitch that comes out is a concert B♭, a whole step lower. This dates back to the early 1700s, when clarinets had only a few keys and could play comfortably in only a handful of keys, so makers built them in many sizes and composers picked the size that suited the music. B♭ and A survived because of their tone and because they fit the keys wind bands and orchestras use most. Music is still written transposed so that the fingerings stay the same on every member of the clarinet family.
Ask a room full of clarinetists why their instrument is in B♭ and you will get a lot of confident shrugs. Most of us learned to play a written C, heard the band tune to it, and never questioned why the piano next to us calls that note B♭. It is one of the most searched clarinet questions online, and the answer is a nice piece of music history.
This article explains what “in B♭” actually means, why the clarinet ended up there, why A and E♭ clarinets exist alongside it, and how to transpose when someone hands you concert-pitch music.
Table of Contents
- What “in B♭” actually means
- The historical reason: few keys, many clarinets
- Why B♭ and A survived and C faded
- Why not just write clarinet music in concert pitch?
- The clarinet family and how each one transposes
- How to transpose for B♭ clarinet
- Does B♭ vs A change the sound?
- Key Takeaways
- FAQ
- One setup for your B♭ and A clarinets
What “in B♭” actually means
The clarinet is a transposing instrument. That means the note written on the page and the note that actually sounds are different. On a B♭ clarinet, every written note sounds a major second (a whole step) lower than written. Play a written C and a concert B♭ comes out. Play a written D and you hear concert C. Your written G is the piano’s F.
This is why a concert band tunes to “concert B♭” and clarinetists play their written C to match it. It is also why an orchestra tunes to concert A and clarinetists play a written B. Nothing is out of tune; the names are just different.
The name of the instrument tells you the concert pitch you get when you play a written C. A “clarinet in A” sounds a concert A when you play written C. A “clarinet in E♭” sounds a concert E♭. The B♭ clarinet is simply the member of the family that became the everyday standard.
The historical reason: few keys, many clarinets
The clarinet was developed around 1700 by the Nuremberg maker Johann Christoph Denner, evolving from an earlier folk instrument called the chalumeau. Those first clarinets had two or three keys. By Mozart’s time in the late 1700s, the standard instrument had about five keys. Everything else was done with the fingers alone, which meant that sharps and flats outside the instrument’s “home” key relied on awkward cross-fingerings that were weak, out of tune, or both.
The solution was not better keywork, which did not exist yet. It was more clarinets. Makers built the instrument in a whole range of sizes, including C, B♭, A, D, and others, each one a slightly different length. A composer writing a piece in E♭ major would call for the B♭ clarinet, because on that instrument the part would be written in the easy key of F. A piece in D major would call for the A clarinet, whose part would be written in F as well. Players carried two or three instruments and swapped as the music demanded.
You can still see this in the repertoire. Mozart’s Clarinet Concerto, K. 622, was written for a basset clarinet in A. Weber’s two clarinet concertos were written for the B♭ instrument. Beethoven regularly wrote for the C clarinet in his symphonies. Each choice was made partly for the key of the piece and partly for the color of the instrument.
Why B♭ and A survived and C faded
Through the 1800s, keywork improved dramatically. Iwan Müller’s 13-key clarinet of around 1812 and then the Boehm system of the 1840s made every key playable on a single instrument. Logically, the C clarinet should have won, because its music would need no transposition at all. It did not. Three things tipped the balance toward B♭ and A.
Tone. Players and composers preferred the sound of the slightly longer B♭ and A clarinets. The C clarinet was widely considered brighter and thinner, and it gradually fell out of favor for anything other than special effects.
The wind band. Military and civic bands grew enormously in the 19th century, and their brass instruments were built in B♭ and E♭. A B♭ clarinet reads in the same written keys as a B♭ cornet or trumpet, which made band music simpler to write and to teach. As band programs became the main way people learned the clarinet, B♭ became the default.
The orchestra. Orchestral repertoire is full of sharp keys, and the A clarinet puts those parts into comfortable written keys. Once the B♭ and A pair covered both flat and sharp music with the same fingerings, there was no reason to keep the C instrument in the case.
Pro Tip: The clarinet’s register key raises the pitch a twelfth rather than an octave. That is a separate quirk from transposition, but it is the reason the clarinet has such a wide range and such a distinctive fingering system compared with the flute or saxophone.
Why not just write clarinet music in concert pitch?
Because transposed notation keeps the fingerings identical across the whole family. The fingering you use for a written C on your B♭ clarinet is the same fingering for written C on an A clarinet, an E♭ clarinet, and a bass clarinet. A player can pick up any of them and read the part without relearning a thing. The instrument does the transposing, not the player.
If clarinet music were written in concert pitch, a player switching from B♭ to A clarinet would have to learn a completely different set of fingerings for every note, and a bass clarinetist would spend their life reading ledger lines. Transposed parts trade a little confusion for the composer in exchange for a lot of simplicity for the player. It is a good trade.
The clarinet family and how each one transposes
Every member of the family is named after the concert pitch that sounds when you play a written C. Here is how the common ones relate to concert pitch:
| Instrument | Written C sounds | Interval from written pitch |
|---|---|---|
| E♭ soprano clarinet | Concert E♭ | Minor third higher |
| C clarinet | Concert C | None (non-transposing) |
| B♭ clarinet | Concert B♭ | Major second lower |
| A clarinet | Concert A | Minor third lower |
| Basset horn in F | Concert F | Perfect fifth lower |
| E♭ alto clarinet | Concert E♭ | Major sixth lower |
| B♭ bass clarinet | Concert B♭ | Major ninth lower (treble clef notation) |
| B♭ contrabass clarinet | Concert B♭ | Two octaves plus a major second lower |
Bass clarinet parts are sometimes written in bass clef, in which case they sound only a major second lower than written, the same as the B♭ soprano. Both notations are in use, so bass clarinetists learn to read both.
How to transpose for B♭ clarinet
Sooner or later someone will hand you a flute part, a hymn from a piano book, or a lead sheet in concert pitch and ask you to play it. The rule is simple: read everything a major second (one whole step) higher than written, and adjust the key signature by adding two sharps or removing two flats.
- Concert C major (no sharps or flats) becomes written D major (two sharps).
- Concert F major (one flat) becomes written G major (one sharp).
- Concert B♭ major (two flats) becomes written C major (none).
- Concert E♭ major (three flats) becomes written F major (one flat).
A few other situations come up regularly:
- Playing an A clarinet part on a B♭ clarinet: read every note a half step lower than written. This is common when a school orchestra has no A clarinets.
- Playing a B♭ trumpet or tenor sax part: read it as written. They are B♭ instruments too. Tenor sax parts sound an octave lower than the clarinet would, but the notes on the page work.
- Playing an E♭ alto sax part: read it a perfect fifth lower than written (or a perfect fourth higher, which puts it an octave up). It is usually easier to transpose from a concert-pitch source if one is available.
The best way to get comfortable is to practice on easy material. Take a hymnal or a book of folk songs in concert pitch and play through a tune a day, reading up a whole step. Within a few weeks the interval becomes automatic and the key-signature swap stops feeling like arithmetic.
Pro Tip: Think in key first, then in notes. If you know the concert key is F and your written key is therefore G, most of the accidentals sort themselves out and you only have to watch for the odd chromatic note.
Does B♭ vs A change the sound?
Slightly. The A clarinet is a little longer, and most players describe its tone as marginally darker and mellower. Composers such as Brahms chose the A clarinet for its color as much as for its key (his Clarinet Quintet, Op. 115, is for clarinet in A). In practice the difference is small compared with the effect of the player, the mouthpiece, and the reed.
What matters more for players who own both is consistency. B♭ and A clarinets use the same mouthpiece and, on standard Boehm-system instruments, the same barrel fit, so a well-chosen setup transfers directly between the two. The intonation tendencies differ a little between the instruments, which is why many players keep a slightly different barrel length for each. Our guide to clarinet tuning tendencies covers how to manage that.
Key Takeaways
| Point | Details |
|---|---|
| “In B♭” means written C sounds concert B♭ | Every written note on a B♭ clarinet sounds a major second lower than written. |
| The reason is historical | Early clarinets had few keys, so makers built them in many sizes and composers chose the size that fit the key of the music. |
| B♭ and A won on tone and practicality | They sounded better than the C clarinet, matched the B♭ brass of wind bands, and between them covered flat and sharp keys. |
| Transposed notation keeps fingerings constant | Written C is the same fingering on every clarinet, so players can switch instruments without relearning. |
| Transposing concert pitch is a whole step up | Read up a major second and add two sharps (or remove two flats) from the key signature. |
| Your setup carries across B♭ and A | The same mouthpiece and barrel fit both instruments, so invest in one good setup and fine-tune the barrel length per instrument. |
FAQ
Is the clarinet in B♭ or C?
The standard clarinet is in B♭. C clarinets exist and are occasionally used for specific orchestral parts or folk music, but almost everyone learns on and plays the B♭ instrument.
Why does the band tune to B♭?
Because most band instruments (trumpets, cornets, clarinets, tenor saxophones, baritones, and tubas) are built around B♭, and that pitch is a comfortable, stable note on all of them. Orchestras tune to A because the strings tune to their open A.
Can I play piano music on the clarinet?
Yes, if you transpose it up a whole step (and adjust the key signature by two sharps) or if you use a version already arranged for B♭ instruments. Many method books and hymnals publish B♭ editions for exactly this reason.
Is the bass clarinet also in B♭?
Yes. The standard bass clarinet is in B♭ and sounds an octave lower than the soprano B♭ clarinet. Its parts are usually written in treble clef a major ninth above the sounding pitch, though some music uses bass clef.
What is the lowest note on a B♭ clarinet?
Written E below the treble staff, which sounds concert D. Some professional models and bass clarinets extend lower.
One setup for your B♭ and A clarinets
Whichever key your clarinet is built in, the mouthpiece and barrel are where your sound is shaped, and a good pair serves both instruments. Gleichweit mouthpieces are made in Vienna for standard Boehm-system B♭ and A clarinets, and the Gleichweit B2 barrel comes in 64, 65, and 66 mm so you can pick the length that centers each instrument’s pitch. If you are not sure which tip opening suits you, the Variety Mouthpiece Test Box lets you try five at home and keep the one that fits.
Now, the next time someone at a rehearsal asks why the clarinet is in B♭, you can give them the real answer: because three hundred years ago it was easier to build another clarinet than another key.
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