yes (its in the same key)
Bass clarinets play in orchestras because orchestras sometimes play pieces that are scored for bass clarinet, or have bass clarinet parts in it. One example of a piece like that is The Rite Of Spring, by Igor Stravinsky. It has significant solos and duets by the bass clarinet, and "the show cannot go on" without the bass clarinet. But most pieces, do not have bass clarinet parts, so the bass clarinet is rarely seen in orchestras today.
Always: Bb soprano clarinets and Bass clarinets, sometimes: Soprano A and Eb clarinets, very rarely: other varieties of clarinet (piccolo clarinet, basset horn, basset clarinet, contra alto/contrabass, alto clarinet, etc.)Bb soprano clarinets (the common clarinet) and bass clarinets are always used in orchestras and bands. Orchestra music (bands not as commonly, but still sometimes) frequently call for soprano A and soprano Eb clarinets, so usually Bb players learn an alternate clarinet and play it when they're not playing the normal Bb part. Other kinds of clarinets, such as basset clarinet, tenor clarinet, and basset horn, are rarely used (not never used, just not nearly as commonly.) Alto clarinets are used much more frequently in bands than in orchestras.
A bass clarinet, like all the different types of clarinets in it's family, have one reed.
Go to the person that fixes bass clarinets
There are bass, soprano, and alto. But there are more than Three sizes! There is the Eb soprano, Bb soprano (most commonly seen), Alto clarinet, Bass clarinet, Contra-alto clarinet, and contra-bass clarinet. There is also an A clarinet!
Not exactly, bass clarinets have five keys at the bottom instead of four, but other than that I think it is the same.
Some people call the bass clarinet and contra alto clarinets "harmony". There seems to be no specific reason.
Clarinets play in treble clef.
No. Clarinets are in Trebel clef, Baritones are in Bass Clef
The clarinet family consists of the E-flat soprano, B-flat which is most familiar. There is also an A clarinet used in orchestral music. On the lower end of the spectrum are the alto, bass and contrabass clarinets.
The members of the clarinet family I am aware of are the B-flat (The most common), the A, the C, and the G. There is also the bass clarinet (In B-flat), the Contra-Alto clarinet, the Contra-Bass Clarinet, and other woodwind instruments.
The bass clarinet, in the form we know it today, was invented in 1838, in Belgium by Adolph Sax, who later invented the saxophone. There were earlier instruments which were clarinet like and that played in the bass register, but they were generally not much like soprano clarinets of the time.