Does everyone have to play in the same key or is the key accustomed to the instrument section? for example, clarinet would use Bb major?

What is a transposing instrument?

  • To be clear. Clarinets are not written in Bb major except when the score is in Ab major. See discussions about transposing instruments. – ghellquist Dec 28 '17 at 9:34

Yes, and no! Everyone sounds like they're playing in the same key, yes, but looking at the actual music in front of the players, no.

There are lots of transposing instruments about, which don't, for many reasons (answered here for several questions) see the music in the same key as non-transposing instruments. An example would be the Bb clarinet, which actually plays a tone LOWER than the written music. So, music for that clarinet needs to be written in a key a tone HIGHER, to compensate.

Horns, likewise, play notes which they may call certain letters, but the sound produced is actually different letters (note names). So, their music needs to be written in keys which transpose what they read into what's actually needed to be in tune with everyone else.

If you look at the score - the music the conductor references - you'll see that even for a passage where everyone is playing in unison, each instrument will have the music written out in the key which makes it sound unison.


This is more of a comment really but I don't have the rep to post it as such.

Whilst I mostly agree with what Tim has said it occurs to me that there is no reason for this to be always true. There are piano pieces where the left hand part and right hand part have different key signatures (e.g. Prokofiev's Sarcasms 3rd mvt), so I would not be surprised if there are orchestral pieces also.

A quick Google search gave this page in Wikipedia - https://en.wikipedia.org/wiki/Polytonality - which cites a number of examples going back to the Baroque period.

  • Marked this up as it's an interesting situation. Can't think why left and right hand should be written (and therefore played) in differing keys though... – Tim Jun 2 '16 at 13:22

The Bb Flat clarinet is a transposing instrument of a whole tone down. Simply put when the clarinet plays a C note what you actually are hearing is a Bb.

So technically the Bb flat clarinet will be notated in a different key than the non-transposing instruments but when you relate it back to concert pitch then it all comes back to the same key.


To add to Neil's comment, given that when the clarinet player plays a C, it sounds like a B-flat, then to compensate, you must tell the clarinet player to play a D so that it sounds like a C - and thus matches the C played by the rest of the orchestra.

If you're writing a piece and are looking to arrange it for band or orchestra, I highly recommend tracking down a copy of the book "Essential Dictionary of Orchestration" by Dave Black and Tom Gerou. You might be able to find a copy at your local library. That's how I found out about it - by stumbling across it at the library (and then I later found a copy at a used bookstore for about three dollars).

Another cool book is "Principles of Orchestration" by Nikolai Rimsky-Korsakov. Rimsky-Korsakov was a famous Russian composer and arranger from time period of the late 19th to early 20th century. So it's cool to see a famous composer talk about how to arrange songs, although you'll probably find Black & Gerou's book to be more useful than Rimsky-Korsakov's.

  • One thing I forgot to mention is that the key that a piece sounds like it is in (regardless of the key signature that is actually printed on the sheet music) is called the “concert key” (if I remember correctly). As I recall off the top of my head… String instruments are ‘concert’ instruments in that you don’t have to transpose their parts. An E-flat on a violin does already sound like an E-flat. So this rule takes care of violins, violas, cellos, and double basses. – Brandon Jun 2 '16 at 14:42
  • On the band side of things, the concert instruments are piccolo, flute, oboe, trombone, tuba, and baritone*. (*Baritone is a weird instrument in that parts can be written in either treble clef or bass clef. Bass clef parts are written in concert key, while treble clef parts are written a whole step higher, like clarinet or trumpet.) As mentioned before, B-flat clarinets must be transposed up a whole step to compensate for the fact that they sound a whole step lower. This rule also applies to B-flat trumpet. – Brandon Jun 2 '16 at 14:42
  • I think French horn parts need to be written a three and a half steps higher. I think bassoons and contrabassons are concert instruments. – Brandon Jun 2 '16 at 14:43
  • Bassoons sounds as written. Most often in bass clef (althought I rather frequently see tenor clef). Contrabassoon sounds one octave below written. Personally I have never seen anythig but bass clef when playing the Contra. – ghellquist May 10 '18 at 20:09

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