Called a variety of names by the various inventors who have iterated on the idea, the 21st century vernacular for that twisty bit at the end of some saxophone necks is “microtuner.” A microtuner is a device attached to or made part of a saxophone neck or a clarinet barrel that is an aid in tuning the instrument.

Broadly speaking, the microtuner and similar devices seek to solve three problems. Firstly, when adjusting the mouthpiece’s lateral position on the instrument, it is easy to knock the reed and ligature around, thus compromising their desired and precise placement. Secondarily, the use of a microtuner can allow a student or teacher to adjust the position of the mouthpiece without touching it therefore lowering the likelihood of spreading germs by contact with saliva. The third, and perhaps most acoustically important purpose is to allow the precise adjustment of the length of the instrument without altering the internal volume of the mouthpiece.

The pitch that a musical instrument produces is primarily determined by the length of the vibrating element. On stringed instruments, it is the effective length of the string. Wind organs have lengths of tubing and brasswinds have tubing of varying lengths that are changeable either by redirecting air through other tubes via the valves or sliding the tubes themselves. When playing a woodwind instrument, the opening and closing of the keys determine the cutoff length of the pressure wave inside the instrument. More open keys mean a shorter wave and higher pitch, conversely more closed keys mean a lower pitch.

When “tuning up” a saxophone, the usual method to alter the overall effective length of the vibrating pressure wave inside of the tube is to move the mouthpiece further on or off of the neck. While this method alters the length of the wave, it also alters the overall volume of the saxophone’s bore. A saxophone is a conical-bored instrument. It is, however, a truncated cone, which is to say that the top end of the instrument is an incomplete cone terminating before coming to a point. In order to complete the cone, the internal volume of the mouthpiece should hypothetically match the missing volume of the cone. 

That hypothetical volume matching creates an issue when tuning the saxophone via the usual push-on/pull-off method: not only is the instrument’s length altered, the mouthpiece volume is also altered. As the neck enters the mouthpiece, it reduces the chamber volume and the opposite happens as it is pulled out.  

While this usual method is functional enough that practically all saxophonists use it to tune their instruments, the altering of the mouthpiece’s bore can cause some tuning issues between the octaves of the instrument or at the extreme ends of the instrument’s range, or can cause other issues such as uneven response across the range of the instrument and inconsistent timbre. What most microtuner devices do, in effect, is to make the volume of the mouthpiece a constant and to vary the effective length of the neck tube itself.

Saxophone necks that feature a microtuner have a length of the neck shaped as a cylinder rather than a cone. On the Conn style tuners, the cylindrical section happens inside of the large twisty bit and the end of the neck whereupon the mouthpiece is affixed is a rather abrupt cone. Others treat the last inch and a half or so of the neck as a cylinder such that a concentric piece of tubing can be slid in and out much like a tuning slide on a brasswind.

Saxophone necks are not the only woodwind devices equipped with microtuners. Conn omitted the microtuner from their Bb Tenor and Soprano saxophone necks, opting instead to affix a tuner into the mouthpiece. A fair number of clarinet models have featured microtuners in the barrel. When a clarinet barrel is adjusted away from the body or the mouthpiece is pulled out of the barrel, an extra gap in the bore is created. While the gap may still be airtight, it means that a small portion of the overall instrument is suddenly wider than the rest. The microtuner barrel solves this by employing the same idea of concentrically sliding cylindrical tubing as the saxophone necks.

While American horn makers had all but dropped microtuners from their saxophones by the 1950s, they persisted on Eastern European and German horns for a couple of decades after. To this day, there are microtuner-type clarinet barrels available on the market. 

Links to Microtuner Patents:

Click Clarinet Tuner: US529817A

Conn Saxophone Tuner: US1308903A

Dillon Tunable Mouthpiece: US2527988A

Gemeinhardt Tuning Slide: US1443112A

Gulick Tuning Device: US1736880A

Leblanc/Beaugnier Tuning Device: FR662866A

Leppe Tuning Device: US1603780A

Loomis Tuning Device: US182655A

Nenneker Tuning Attachment: US1374758A

Pan American Tuning Device: US1870211A

Simpson Tuning Clamp: US1549617A

Sinclair Tunable Mouthpiece: US1361629A

Solberg Clarinet Tuning Slide: US1194887A

Todt Tru-Bore Tuning Device: US1867481A

Twist n' Tune: US8283540A

Van Caster Tuning Joint: US2943526A