Sometimes there will only need to be a few b flat clarinets, and other times a few of each type of clarinet is needed. In even some cases you may need 25 or more clarinets. It all depends on the writer of the music and how dominate he or she wants the focus on the woodwind section containing the clarinet. Another factor contributing, is the amount of space on the stage in which the orchestra is performing. If there isn't a lot of room then the organization will range from left to right, most important to least
Sometimes there will only need to be a few b flat clarinets, and other times a few of each type of clarinet is needed. In even some cases you may need 25 or more clarinets. It all depends on the writer of the music and how dominate he or she wants the focus on the woodwind section containing the clarinet. Another factor contributing, is the amount of space on the stage in which the orchestra is performing. If there isn't a lot of room then the organization will range from left to right, most important to least