All players of the clarinet family have always envied the facility of the flute players as they effortlessly flip around on their instrument, making repetitive octave jumps with great facility and ease. Of course, clarinet players achieve the same facility, but only with much, much more practice, because the clarinet is cursed with the dreaded "break".
For the clarinet family has been cursed by the science of acoustics to be different from the other members of the woodwind family. As the cylindrical clarinet family overblows to the twelfth (instead of the octave as does every other woodwind instrument), there is a gap of more than an octave of the extra five semitones on the instrument are produced by the clarinet equivalent of the palm keys, the Ab and A key (each of which produces their namesake note), plus the register key (to produce the Bb when fingered along with the Ab/A key combination.
(Having these "in between" keys is nothing new, for most instruments have a number of extra keys towards the upper end of the instrument, this to ease operations between the registers of the instrument. But, the clarinet could not exist without them; they are not just a convenience.)
Where the clarinet has always suffered in this regard is with the throat tones, specifically the dreaded "throat Bb". since the days of the two key clarinet, the fingering for Bb in the staff has always been the "pinch" of the A/Ab key ganged together combined with the register.
But, the note thus produced has always been a compromise, and not the best of compromises as well. Every musical instrument is a maze of compromises, and the clarinet is no exception. Each tone hole has been tweaked so as to function well with the others with which it is required to act in concert.
But, the Bb in the staff is different. When fingered in the historic fashion, the tone hole from which the note is emitted is the narrow little register vent. Aside from being too narrow for the purpose, it also has the disadvantage of being located on the back of modern instruments. (This is, I suspect, one of the reasons that the register vents of Albert, Oehler and older Boehm instrument were located on the front of the horn.)
Nevertheless, for many years clarinet players soldiered on, utilizing various trick fingerings to resonate and shade the horrible throat Bb. As the simple clarinet became the Boehm instrument and other alternate fingerings were added, a trill key located on the upper right side of the instrument added a tone hole that was perfectly located and sized to sound a "true" Bb. However, the finger that operates that key can only be in one place at a time, so the register key remained the "main" method of obtaining the Bb.
Then, along came the likes of Antonio Romero y Andia and Rosario Mazzeo. An Spaniard and an Italian-American respectively, they put their collective feet down and said that this situation should not stand.
Romero was first. He took the Boehm instrument, more or less retained the arrangement on the lower joint, but added a series of sprung shut keys at the upper end of the instrument. These keys were operated by rings on the lower joint of the instrument, producing pure and clean throat tones. Here's a photo of one:
However, the Romero instrument has so many rods and levers that it looks like a miniature bass clarinet with a bad skin condition. And, all of that clever key work requires no less than fourteen adjustment screws, making for an oboe-like nightmare of an instrument.
Rosario Mazzeo, a long-time bass clarinetist (and thus related to the most perfect instrument of all time) took another approach. He noted that the perfect tone hole to vent a throat Bb already existed on the Boehm instrument (in the agency of the second trill key from the top), and set about to find a way to operate it without tying up that critical first finger on the right hand. While he was at it he covered the thumb hole with a plateau key:
…(Why? I don't know…) and eliminated the bell ring (to cut down on the weight of the instrument). The result, summarized in US Patent 2,867,146, has been immortalized as the Mazzeo System clarinet:
And, like all clarinets that differ from the bog-standard 17/6 Klose-Boehm clarinet, it landed in the clarinet world with a resounding "plop". Manufactured by Selmer in their professional, intermediate (Signet) and student (Bundy) lines, Mazzeo instruments enjoyed a very brief surge of interest in the 1960s, only to largely disappear from sight. Why?
As far as I can tell, there are several problems with the Mazzeo instrument. The first and foremost of these is that the Mazzeo instrument is just plain different. Musicians are by and large a conservative lot, and they generally learn at the feet of someone who has learned before. The additional facility of the Mazzeo instrument was not sufficiently great to overbalance the added learning curve and additional cost of the Mazzeo instrument.
Mazzeo recognized this, and he made provisions with his designs to ensure that the Mazzeo key work could be disconnected at will. But, by doing so, he unknowingly added an additional problem with the instrument, the ability to remove the easily removed operating parts so that his key work would no longer function.
I own precisely one functioning Mazzeo instrument, a Selmer (Paris) Bb soprano with the bare minimum system installed. (Mazzeo also caused "full Boehm" Paris versions of his instrument to be created.) I have bought about seven Mazzeo instruments over the past twenty years, but in each and every case the Mazzeo aspects of the horn have been disabled, with critical parts (either the "clutches" (there are two on the Paris instrument, one on the others) or a rocker arm) missing.
The third problem with the Mazzeo instrument is that repairmen are not very familiar with the operation of the lower rings that open the "Bb" tone hole. On the Paris horn, there is an adjustment screw to help with this; not so on the Signet or Bundy versions of the instrument. Getting everything balanced out just so requires a bit more attention than the typical technician is going to want to give.
That said, there is nothing inherently "wrong" with the Mazzeo instrument. To enable the Mazzeo features on the Paris instrument, you disengage two "clutches", one behind the A key touch piece:
…and one attached to the second trill key from the top:
By doing so, you change the instrument from a standard 17/6 Boehm horn to the Mazzeo.
Once so enabled, the throat Bb, emitted from one properly placed and sized tone hole on the side of the upper joint, is as clear and resonant as the other notes on the upper joint of the instrument. Mind you, the regular Bb (LT and A key) is also relatively clear on this instrument. But the Mazzeo one is clearer.
The standard Mazzeo fingering for Bb in the staff is the A key plus any or all of 123 on the right hand. This has the happy coincidence of readying your right hand for the B natural and C above the staff, simply by dropping your left hand into place. Since the first finger left hand does not have to move from the A key, the biggest issue with the break is completely eliminated. However, you do need to break yourself of resonating the G, Ab and A with your right hand.
The reconversion of the instrument from Mazzeo to non-Mazzeo clarinet takes about ten seconds, and requires both hands to execute a relatively fiddly series of moves as you first slip the little knurled wheel attached to the A key to the right, and then slide the trill key clutch towards the top of the instrument. It's a little cumbersome, particularly with the "sticky" trill key clutch.
Has the Mazzeo instrument replaced my "everyday" player clarinet (a Selmer (Paris) 21/7 "full Boehm" instrument)? No way, buster, for I get far too much use out of the auxiliary Eb lever and articulated G# of the 21/7. However, offer me one of Rosario's full Boehm instruments, and you might change my mind.