Why do Bb-instruments exist?

[jkristiand]

For a long time I've been wondering how come instruments like
trumpets, sax's and clarinets have this Bb tuning.
Why weren't they just tuned like ordinary instruments to begin with?

I find myself unable to find a reasonable explanation. I hope some of you can
help me understand 

Jkristiand

[Floristan]

From the Columbia Encyclopedia (hope this helps):

Transposing instrument:
   
A musical instrument whose part in a score is written at a different pitch than that actually sounded. Such an instrument is usually referred to by the keynote of its natural scale—the clarinet in A, for example—in which case A is sounded when the tone C appears in the musical notation. Since A is a minor third below C, the part for this instrument must be written a minor third higher than it is to sound. Transposing instruments were necessary in the 17th and 18th cent. when the natural brasses and the clarinets could be played easily in only a few keys; they were therefore built in specific keys. Although improved construction in the 19th cent. obviated this necessity, all clarinets, the English horn, oboe, French horn, trumpet, alto flute, cornet, and most saxophones are transposing instruments. Parts for the piccolo, double bass, and contrabassoon are written an octave below or above actual pitch to avoid ledger lines, but this is not, strictly speaking, transposition.

[BoliverAllmon]

I was told that certain instruments were hard to play in certain keys due to fingering, so they made instruments that C maj fingering (which was the easiest) was actually sounding in a different key.

[pianodoc]

Another reason is so that "like" instruments from the same family can finger the "same" notes the same way.  Saxophone - soprano, alto, tenor, bari, bass - put three fingers down you will play a G - even if it comes out a different note in concert pitch; because each plays in a different range from low to high.

Kindof like the midi pitch adjust that is possible.  If you know the piece in one key, and need it to sound in another, you won't need to re-learn, or re-finger a piece.

[BoliverAllmon]

Another reason is so that "like" instruments from the same family can finger the "same" notes the same way.  Saxophone - soprano, alto, tenor, bari, bass - put three fingers down you will play a G - even if it comes out a different note in concert pitch; because each plays in a different range from low to high.

Kindof like the midi pitch adjust that is possible.  If you know the piece in one key, and need it to sound in another, you won't need to re-learn, or re-finger a piece.

yeah like that.

[timothy42b]

Long ago it made things easier.

Instruments were not chromatic.

So you had different ones for playing in different keys, or at least inserted different crooks to put them in those keys.

Then you changed the transposition of the printed music to that key, and it was easier on the player.  You find trumpet parts in Bb, B, C, D, Eb, probably a lot more. 

Now, however, modern players will often play them all on the same instrument, and now they have to do the transposition mentally.  The old parts are still written in those keys, and it can make it much harder. 

[pocorina]

Seems dumb to me. I can never cope with it, whilst accompanying my clarinetist friend.