About clarinet mouthpieces

Mouthpiece and the reed make the clarinet sound. Reed is attached to mouthpiece by ligature.

When musician  blows into the clarinet, reed vibrates and that makes the sound. Mouthpiece defines the sound and ligature must be at the right place, otherwise the reed has problems vibrating.

The top of the mouthpiece (clarinet players put in their mouth) and the top of the reed are 1mm apart.

The difference in this distance must be very exact. This distance is approximately between 1.000mm to 1.040mm. There is a lot of different mouthpieces on the market and the technology  must be very precise to make them. I use Selmer mouthpiece, but there are many more brands like Vandoren, Yamaha...
You can take a look in this online store for more info about Clarinet mouthpieces (Brands, price and such)
The difference between closed and open mouthpiece is:
- closed mouthpiece has a smaller tip opening
- on a open mouthpiece clarinet players use less hard reeds
I started to use a closed mouthpiece when i played 3 years, because my tutor said that i would make better sound with harder reeds. I found out that on my closed mouthpiece best reed hardness is 4.5(Vandoren silver). Depends on a reed brand. I also used reeds with hardness 4.

About clarinet reeds part two

Beginners shouldn't try a reed that is harder than a 2.5. Harder reed means that sound is harder to produce.
Students should wait until they have developed (some years of  practice) before trying harder reeds.

French reeds like Vandoren V-12 advanced Bb clarinet reeds are cut thin, but slightly thicker than American reeds at the bottom of the reed. This makes them slightly harder to play on, but produces a rich, better sound. The tone is also brighter.

German reeds (Vandoren's Blackmaster reeds, and other non-major brands) tend to be cut thicker, particularly in the center of the reed. This type of reed, played properly, produces a dark, rich, but not versatile tone.
German reeds are ment to be played with a German mouthpiece.

American reeds try to combine the French and German sound, to get a dark tone with plenty of flexibility. American mouthpieces have much wider tip openings and are larger. The reeds are cut with a thinner bottom and center. This type of reed is very good for students .

Reeds must be stored carefully, in a case hey came in, or in a case made for reeds, must be dry and don't expose them to high temperature changes.
If you store a reed wet and sometimes weather changes can cause the reeds to warp (Reed is warped if you look at the tip of it and it seems wavy). Often can still be played on, but they'll be more difficult and won't sound very good.
Reeds should be thrown away if they are chipped or cracked.

To test the reeds i normally buy a 10 pack and try all of them for 10 minutes.I put the ones i don't like back in the box. I do the same thing that the next day (next time). I  get 2-5 good reeds from a box of 10. Depends on a brand. At the moment i am using 3 Vandoren's reeds V-12 strenhgt 4 and 1 reed strenght 4.5.

Reeds are very important, because they produce clarinet's tone. Choose the appropriate reed for your mouthpiece, and keep your reeds in good condition.

About clarinet reeds

The clarinet reeds are made from the cane of Arundo donax, a type of grass. Reeds may also be manufactured from synthetic and plastic materials.
Brands of reeds are:

Rico, Mitchell Lurie, Vandoren, D'Addario ...(few other brands).
All of these brands make several different varieties of reeds, in different strengths.

Reeds come in varying degrees of hardness, generally indicated on a scale from 1 (soft) through 5 (hard).  
Reed and mouthpiece characteristics work together to determine ease of playability and tone characteristics.

B clarinet reed measurements are approximately:
tip - 12 millimetres  wide
lay - 15 millimetres long (distance from the place where the reed touches the mouthpiece to the tip)
gap - 1 millimetre  (distance between the underside of the reed tip and the mouthpiece).

Theory of sound.
The ligature fastens the reed to the mouthpiece. When air is blown through the opening between the reed and the mouthpiece, the reed vibrates and produces the instrument's sound.
Reeds all look the same, but they aren't. They are produced from different qualities of cane, and cut slightly differently. Fractions of millimeters in the cut and the differences of the sound is amazing.

History of clarinet

It was invented around 1690. Clarinet developed from a instrument called the chalumeau.
This instrument was similar to a recorder (of the family fipple flute), but with a single reed mouthpiece and a cylindrical bore.
Around the turn of the 18th century the chalumeau was modified by converting one of its keys into a register key to produce the first clarinet.
The final development of the clarinet used in most of the world was introduced by Hyacinthe Klose in 1839.
Klose was so impressed by Boehm's invention (flute developer Theobald Boehm) that he named his own system for clarinets the Boehm system, although it is different from the one used on flutes.
Gradually it became the standard, and today the Boehm system is used everywhere in the world except Germany and Austria, there still use a direct descendant of the Mueller clarinet known as the Oehler system clarinet.
Some Dixieland and Klezmer style players still use Albert system clarinets, because of simpler fingering that allows easier  gliding over the notes.