The combination of the mouthpiece and reed is the most important part of a clarinet. The next most important piece is the barrel, and then the first keyed joint. The importance decreases, so that the bell could be made out of paper mache and no one would be able to tell the difference.
Beginning to intermediate level mouthpieces
If your son or daughter is starting out on clarinet, please don't frustrate them by skimping on second-rate reeds or a cheapo mouthpiece! They will probably be successful with any good-working instrument if they have a good reed and mouthpiece.
Some people think it is better to start beginners with a mouthpiece that has a more open facing, like the first two below. This allows the student to use a softer reed and still get a nice, round sound. Here is a list of good, inexpensive mouthpieces for less advance players. I think plastic mouthpieces are fine for beginners. For intermediate players, go with one of the hard rubber ones below.
NEVER stand a clarinet up on the floor on its bell! Always use a clarinet stand or lay it somewhere. I have seen many clarinets fall, and it results in a broken mouthpiece about 50% of the time!
If you are a more advanced player, you will want a hard rubber mouthpiece. They sound better and last longer, and the good ones start at about $70.
1July2012: I have changed to the Chedeville Prime mouthpiece for my performing and reviewing of clarinets at this site. It gives me a more focused sound, more overtones, and probably a little less open but longer facing than my Vandoren B45. Two mouthpieces that are somewhat similar are the Tom Ridenour TR-40 (a little more closed), and the Portnoy BP02. The Portnoy BP02 is a little softer, mellower, and perhaps has a bit less focused sound. I carry the Portnoy as my backup mouthpiece. See my review at clarinetpages.info. See the Chedeville sub-page with information from my e-mail conversation with Omar Henderson.
[May 2013] I ordered a second Chedeville Prime because I was so happy with my first. However, when I got the second one, it did not play nearly as well as the first. Eventually, when I realized the problem, I sent it back. Omar Henderson replaced the mouthpiece for free. The second one plays better, but not up to the level of my first one. I thought that the computer guided machining process for the Chedeville line would make for great consistency. Evidently NOT! I recently played a Vandoren 5RV Lyre that plays almost like my first Prime mouthpiece, and probably more like it than the Portnoy BP02. (The VD might have that .06mm difference in tip opening shown in the specs below.)
During the days I was in grad school and teaching music, I played on a Hite D mouthpiece (tip opening .041"). Sadly, David Hite passed away, but his mouthpieces are still being marketed, and the prices seem quite reasonable. I haven't heard if the quality has gone down. I have one that I purchased after David's passing, and it plays like my other two. These days I hear great things about Fobes mouthpieces. The Hite mouthpieces don't seem to play well with my Legere Reeds.
No name mouthpieces are not always bad. If it is plastic (with a very shiny appearance), then it is doubtful that it will be good. Some hard rubber no-name mouthpieces that came with French “stencil” clarinets are excellent.
For Advanced Students:
All are made of hard rubber. There are many fine makers and models that I have not listed.
For a good chart for Vandoren mouthpieces, see saxplus.com.
New information that I need to verify: Concerning the B45 moutnpiece that I use:
It's important to note that Vandoren Traditional mouthpieces are constructed to play at A=442, rather than the American standard of A=440. To get an A=440 tuned Vandoren one has to specify the "13 series".
Here are my general comments on the Vandoren BD5 mouthpiece:
Until now (April 2017) I have been playing on a Chedeville Prime mouthpiece, from Doctor's Products. It is excellent and I still highly recommend it. But I wanted to see how I liked the BD5 so that I could say whether or not I recommend it on the Mouthpieces page of clarinetpages.net. I DO recommend it!
The packaging says, “The perfect balance between a dark, rich, yet compact sound.” My first impression is that this feels much more open mouthpiece than my Chedeville Prime, and that it has a less compact sound. That's not a bad thing. My sound on the Chedeville could be at times become more compact and bright than I liked. I wanted to make sure that the BD5 did not have the throat-tone flatness that I experienced with my Vandoren B45 mouthpiece (especially when playing a Legere reed). [Update December 2017: The BD5 can be slightly flat in the throat tones when playing loudly, but not as bad as the B45.] If I want a more centered sound with greater bite and projection, the Chedeville would be my choice. Playing in a chamber music situation, the BD5 will be lovely. Because of that open free-blowing feeling, I think that the BD5 will be great for jazz, yet— with a reed and embouchure change, move right onto the classical music stage.
The box claims that the BD5 has a medium facing with a 113 tip opening— as it would be commonly called. (Better stated as 1.13mm.) They also suggest a 3 to 3.5 reed for the mouthpiece. I currently play a 3.5 Legere Signature reed with this mouthpiece when I am playing my A clarinet. (This is partly because the A clarinet is naturally a bit more stuffy.)
So I agree with the Vandoren company that the BD5 is perfectly balanced. And the $129 price point is also an excellent price for a professional clarinet mouthpiece.
Crystal and Poly Crystal mouthpieces:
I just had an opportunity to try a James N Pyne * Clarion Poly Crystal mouthpiece. It is beautiful, but I hated the way it played. I didn't like the sound or the response with my Legere Signature 3 3/4 reed.
Poly-crystal is evidently some kind of plastic. It doesn't feel at all like the cool glass feel of traditional crystal mouthpieces. The traditional crystal breaks easily when dropped. The poly-crystal won't have that problem. From a long time ago when I tried a real crystal O'Brien mouthpiece, it had a quick response and kind of a hollow sound.
Portnoy 3 has a nice open facing and should work well for this.
Brillhart 3 or 4
The older Brillhart mouthpieces were better for both clarinet and sax. Here is an example. Actually this old #2 would be great for jazz.
Many other measurements and technical information is found in this article at ClarinetPerfection.com.
See this thread about beginner mouthpieces at woodwind.org.
How to measure mouthpiece facings, discussed at woodwind.org.