Last issue, I reviewed new 12-hole chromatics from Bends, Seydel, and Suzuki. This time, I'm going to review two models that represent updated versions of two long-standing Hohner models, the 270 Deluxe and the CX-12 Jazz.
For many years you could only buy a few models of chromatic harmonica, all of them from Hohner. Over the last few decades, Chinese manufacturing has given us many low-priced harmonicas, while high-quality harmonicas at a variety of price points have appeared from Suzuki and Tombo in Japan, Hering—and now Bends—in Brazil and, with the fall of the Iron Curtain, Seydel in eastern Germany.
How has market leader Hohner responded to these challenges? Basically, by improving quality (and quality control) in their existing models, and by introducing new models that either embody new designs, such as the CBH 2016 and the CX-12, or that offer improvements to existing designs, as with the 270 Deluxe and the CX-12 Jazz.
A Few Basic Concepts
In case you're not yet familiar with them, chromatic harmonicas have several features not present on diatonic harmonicas.
- Windsaver valves are little strips of plastic mounted to keep air from leaking around a reed that isn't being played. In any given hole, there is one reed activated by inhaling and one by exhaling. The valves keep the draw (inhale) reed from leaking air when you exhale, and keep the blow (exhale) reed from leaking air when you inhale. That way the tone of each note is stronger and you need less breath to sound each note.
- The mouthpiece is a strip of metal that covers the front of the harmonica and is shaped to fit your mouth. Each hole in the mouthpiece leads to two more holes in the body of the harmonica (more about that in a moment).
- The slide assembly consists of two or three layers of metal grids, each with a checkerboard pattern of square or rectangular holes. The slide assembly fits behind the mouthpiece, just in front of the body of the harmonica. One of the grids is called the slide because you can slide it from left to right by pressing on a button that sticks out of the right side of the harmonica. If the harmonica is in the key of C, you'll get the notes of the C major scale until you press the button to shift the slide to the left. The slide will then cover up the holes that lead to the reeds for the key of C and instead open a second set of holes that lead to the reeds for the key of C#—that's why each hole in the mouthpiece covers two holes in the harmonica, one for the notes of C and one for the notes of C#. The notes of those two keys give you all the notes you need to play any scale in any key.
- A chromatic can be cross tuned or straight tuned. A straight tuned chromatic has all the notes of the C scale on top and all the notes of C# on the bottom. With the slide out, all the open holes are on top, as shown in Figure 1.
With a cross tuned instrument, the keys of C and C# alternate between top and bottom. Consequently the open holes in the slider also appear in an alternating pattern, as shown in Figure 2.
Cross tuned instruments have bigger holes in the slide, allowing for more air to pass through to the reeds. However, the wider holes in the slider require that you push the slide farther to change between C reeds and C# reeds. For fast playing, you may have to work harder to attain speed with a cross tuned chromatic.
Mouthpieces, slides, and valves help the chromatic harmonica to do things that other types of harmonicas can't do, but they also introduce a whole set of problems that other harmonicas don't have:
- The shape of the mouthpiece and the mouthpiece holes can be comfortable or uncomfortable for your lips and tongue. In addition, an abrupt change of slope where the mouthpiece ends and the covers begin can affect how airtight a seal you can make between your lips and the harmonica when you cover a wide area on the harmonica with your mouth.
- Slides can stick, or grind against the other metal layers in a grid, and they can move sluggishly. If the mouthpiece is loose, the slide can leak air and weaken the tone of the instrument.
- Valves can stick, pop, and buzz as they get wet or collect sticky residues from player's saliva and residue from food and drink.
In addition to features, performance, looks, and price, we'll examine mouthpieces, slides, and valves of the harmonicas under review.
About the Manufacturer
Hohner is perhaps the world's greatest success in the harmonica business. While they've been around since 1857, they're not the oldest. But their long success began with an early grasp of the need to control their international marketing and distribution, coupled with an aggressive competitive attitude which led them to absorb many competitors, and an absence of the family strife that ended the success of some of the other early family-run harmonica businesses. And despite the popular sport of Hohner-bashing, Hohner has always used components—especially reeds—that set the quality standard by which all others are measured.
(By the way, you can read a fascinating account by Hartmut Berghoff of how Hohner attained success in the 19th century marketplace at http://es.oxfordjournals.org/cgi/reprint/2/2/338)
About the New Hohner Chromatic Reed Designs
Starting in 2005, Hohner has made changes to the reeds used in their chromatics, and this has occasioned some concern in the player community. As long as I'm writing about Hohner chromatics, I decided to seek some information on this. I got some historical perspective from Rick Epping, former US product manager and designer of the XB-40 diatonic, and additional information from Steve Baker, who was able to relay information from Hohner Germany.
To start, I should explain the German word Mensur as explained by Steve Baker: “Hohner uses this term to refer to the physical dimensions of the reed—length and width. With any given Mensur you can make the reed sound at different pitches through the type of profile milled into the upper edge of the reed, i.e. the variation in thickness throughout the length.”
When Rick Epping was designing the XB-40, which is about the same size as a 10-hole chromatic, he relates, “I chose the Knittlinger Mensur used for the Auto Valve for the XB-40 reeds, which differed from the Chromatic Mensur in that the narrow, 1.9mm reeds began at a longer length than they did on the Chromatic Mensur, and had a better response than high reeds that were 2.1mm wide. This Mensur was subsequently adopted for the chromatics for the same reason.”
As to reed materials, Steve relates that “The reed material has been the same for several years now and is used on all models made in Trossingen.” He answered further questions as follows:
How are the new reeds different physically and in materials?
Steve: The material is the same as it's been for years. The new Mensur initially introduced with the XB-40 and gradually implemented on all Hohner Classic chromatics features narrower reeds from the 8th channel of a 12-hole upwards. As of around 2006, new reed profiles similar to those introduced in 2005 on Hohner Classic diatonics were also introduced for chromatics.
What benefits do they offer to the player?
Steve: Mechanical tests in the factory showed that the narrower Mensur improves response on the high notes and also extends reed life. The current reed profiles have extended reed life considerably and have greatly reduced the incidence of actual reed breakage.
When were they introduced for chromatic models?
Steve: See above. Due to the time lapse between introducing a new manufacturing process and it finally ending up with the player, it's very difficult to quantify this exactly and there's always the possibility that old stock is laying around somewhere, which confuses the issue. The change in chromatic Mensur was introduced gradually, model for model, whereas the new profiles were brought in across the board, though they were first introduced on diatonic models and later incorporated into chromatic production.
If you look at the reedplates on your harmonica, you'll see a 4-digit number. The last two digits are the year of manufacture. If an “X” precedes the number, you have the newer reed design. This means that if you need to replace a reed from Hole 8 to Hole 12, you won't be able to use older reeds.
Hohner 270 Deluxe
Starting in the 1920s, the original Hohner Super Chromonica (Model 270, originally called the 260½) defined the appearance and construction of the twelve-hole chromatic harmonica. Over the years, both Hohner and its competitors have often based their new chromatic models on the 270, including such current Hohner models as the Larry Adler, the Toots Mellow Tone and the Toots Hard Bopper. The 270 is a straight-tuned 12-hole chromatic with a three-octave range. The model in C has Middle C as the lowest note. Other keys are tuned lower in pitch than the C, reaching down to a tenor C that is pitched an octave lower than the regular C.
Like many players, I learned to play chromatic largely on the 270. I had already played the larger 16-hole models but found them a little ponderous and stodgy. When I got a 270 it was the chromatic equivalent of getting my first Marine Band. It was so responsive that I could feel the cover plates vibrating in my hands. The tone was warm, full, and flexible, and the notes bent easily: I fell in love.
But while the classic sound and appearance of the 270 have been highly valued by both professional and amateur musicians, two aspects of its design have always bothered players. The reedplates were fastened to the comb with nails, making it hard to disassemble the instrument for servicing. And many players found the square holes abrasive to the tongue.
Over the years, players have taken matters into their own hands to improve the 270 rather than switch to a competing model. Some would retrofit their 270s with round-hole mouthpieces taken from Hering or Suzuki instruments. And some would either drill out their 270 combs and reedplates for screws, or even design and build new combs out of plastic or even stainless steel.
After following the 270 with many newer designs over the years—the Chrometta, Amadeus, Meisterklasse, CBH 2012, and CX-12—Hohner at long last has taken another look at its still-enduring original design. Both the 270 and the Marine Band have benefited from this review. For the 270 Deluxe, screw construction and a round-hole mouthpiece have been the results, together with two features borrowed from the Toots Hard Bopper—thicker reedplates (1.2mm instead of 1.05) and longer reeds.
Presently the 270 Deluxe comes only in regular C, with no options presently for a tenor or for other keys. (However, Harmonicas-Direct in the UK is already listing the 270 Deluxe in G as well as C, so other keys may soon follow.) If you want additional keys, you can retrofit any existing 270 with the round-hole mouthpiece of the 270 Deluxe. Hohner USA sells them for $34, while harponline.de has them for €28.50. However, to convert regular 270 reedplates in other keys to screw together on 270 Deluxe comb, you'd need to drill them in the correct spots and obtain the required screws. If you're handy with a drill press, you can go this route, and the screws are available from Hohner USA. Harponline.de sells a complete conversion kit with step-by-step instructions, but follows a different screw placement pattern from the 270 Deluxe.
As of this writing (October 2009) the standard 270 Super Chromonica has a list price of US$196 and can be found online for $140–$150. The 270 Deluxe lists for $254 and can be found online for about $170. The screwed-together construction and round-hole mouthpiece easily justify the $30 to $50 price difference, as both the labor and materials involved for a do-it-yourself upgrade would easily cost much more.
By the way, international comparison of pricing for Europe and the UK yields the following prices:
USA: MSRP $245. Street price approx. $150 to $175
Europe: Harponline.de: €124 (approx. $185)
UK: Harmonicas-Direct: £99.99 (approx. $164)
Hohner CX-12 Jazz
When the CX-12 was introduced in 1991, it was a revolutionary design in chromatic harmonicas. Its construction emphasized simplicity of construction and ease of disassembly. The central block of the harmonica—the comb and reedplates—we held inside the shell by a tension bar across the back that could be removed by thumb pressure. And the slider was held in place by a simple hook on the slide button that allowed for easy removal of the slide for cleaning—no more unscrewing a four-layer mouthpiece assembly to get at the slide, or keeping multiple small parts in alignment while you reassembled it.
The CX-12 is a cross-tuned 12-hole chromatic. As with the 270, the default key is C, with lower-pitched models ranging through various keys down to a tenor C model. It is renowned for being unusually airtight, loud, and responsive, and for its ease of note bending relative to other chromatics to note bending.
A little-known part of the story is that the CX-12's quick and easy disassembly without tools was inspired by modern automatic weapons design. The late Horst Jakubaschk was head of research and development for Hohner at the time (end of the 1980s and into the 1990s). He had previously designed weapons for firearms manufacturer Heckler & Koch. Rick Epping, designer of the Hohner XB-40, relates, “An intelligent and gentle man, Horst told me he left H&K for Hohner for ethical reasons, preferring to assist in the development of music rather than war.”
One aspect of the original CX-12 design that wasn't quite fulfilled was that the radius of the mouthpiece was originally intended to be smaller and thus easier to fit in the player's mouth. However, at a certain point in the design process the material was changed from plastic to metal, which required increasing the radius. When the material was changed back to plastic, the larger radius was retained, resulting in the present shell used in the CX-12 black and gold models. The new CX-12 Jazz offers a reduced mouthpiece thickness by giving the appearance of carving out part of the radius of the existing shell.
The new Jazz shell is the only part of the CX-12 Jazz that differs from the current CX-12 black model. The CX-12 black has a US list price of $250 and sells for about $170, or about the same price as the 270 Deluxe. The CX-12 Jazz lists at a whopping $450 and is offered for sale in the $300 to $315 range. The buyer is being asked to pay an extra $140—about 82% of the selling price of the CX-12 black—for a simple change to the cover shape.
Presently the CX-12 Jazz is offered only in regular C. If you want a tenor or a different key, you can obtain and install reedplates in that key (reedplates sell for about $113 in the US, or €80 from Harponline in Germany). Alternatively, you could fit a Jazz shell to an existing CX-12. However, it's an expensive option. This may change, but presently the Jazz shell can be found in the US for between $225 and $250, while Harponline.de has it for €85, or about $127. (The higher US selling price originates in Germany, not in the US.)
Internationally, pricing for the CX-12 Jazz appears to be fairly consistent. Harponline's lower price will be offset for North America by the shipping cost:
USA: MSRP $450 Street price $300 to $315
Europe: Harponline.de: €184 (approx. $275)
UK: Harmonicas-Direct: £189.99 (approx. $312)
Opening the Box
|The 270 Deluxe comes in the familiar hard plastic coffin box that has been used for the 270 for several years, but in black instead of green. This is a practical, compact box that protects the harmonica, is not easily susceptible to cosmetic damage, and doesn't take up too much space.
|The CX-12 Jazz shell is too large for the 270 box, and rather than design a new box for the CX-12 line, Hohner simply adapted the box it uses for sixteen-hole chromatics. This box affords the harmonica good protection while saving manufacturing costs for Hohner. However, the box is much larger than it needs to be, with the disadvantage that it takes up valuable space in a player's gig case. Considering the premium price Hohner is asking for the CX-12 Jazz, a box that doesn't waste space might have helped add value for the end user.
That First Thrilling Glimpse
The 270 Deluxe has the familiar shape that has delighted generations of harmonica players. However, the new graphics on the top cover and the smooth round mouthpiece holes freshen and enhance its appearance.
The CX-12 Jazz presents a dazzling appearance with its coppery-gold metallic finish and the sleek lines created by the mouthpiece indentation that appears to be scooped out of the front of the shell.
Picking It Up
The 270 Deluxe is listed as weighing 195 grams (about 7 ounces), which is 15 grams more than the regular 270. This may be an error, as the Deluxe seems to have nothing that would increase its weight. The shell formed by the covers extends only over the reeds, making the hand cupping area as compact as possible. The total height at the rear of the instrument is noticeably slimmer in the hands than the CX-12 Jazz, which some players may prefer.
Holding comfort, unchanged from the original 270, is somewhat compromised by sharp comb corners, reedplate edges, and cover edges. It would be nice if Hohner smoothed these edges at the factory. However, considering the relatively low price of the 270 series, this instrument delivers value in other ways, and the player can easily smooth these edges with a file or sandpaper.
The CX-12 Jazz, like other CX-12 models, weighs in at a quite manageable 195 grams (slightly less than 7 ounces). It is comfortable to hold, having the advantage of smooth surfaces and rounded corners and edges—there is nothing sharp to poke, scrape or cut the hands or mouth, and the shell offers no crevices for air leakage or trapping moustache hairs. While the air space under the shell runs the full length of the harmonica, the bell-like flare in the center allows for effective hand cupping to shape sound. The slide button surface is large and textured to prevent finger slippage, and has rounded edges—again, nothing sharp.
Putting it in Your Mouth
The rounded, smooth-edged holes of the 270 Deluxe are immediately noticeable. The profile of the mouthpiece is also comfortable. However, when playing wide tongue-blocked intervals, the bump presented by the front of the covers can disrupt the seal of your embouchure. This is simply endemic to the 270-based design, and the player has to adapt to it and work to minimize or eliminate any leakage.
The one-piece shell of the CX-12 Jazz, coupled with the slimmer mouthpiece profile (only 11mm tall at the front, comparable to the 10mm front thickness of a 270), make it easy to get the harmonica deep into your mouth with no disruption of embouchure seal. The smooth surface of the shell glides easily in the mouth.
When I first saw a photo of the scooped-out mouthpiece area of the CX-12 Jazz shell, I couldn't help noticing that the right and left ends of the mouthpiece flared upward to return to the full thickness of the original CX-12 front. I wondered whether this might not disturb a tongue-blocked embouchure. For instance, if you tongue block with the opening in the right corner of your mouth and play Hole 1, your lips and tongue will be trying to maintain an airtight seal over an irregular surface, where the mouthpiece flares back to the original thickness. However, when I tried playing this way, I found that the ends of the mouthpiece presented no problem in maintaining a good seal.
The Slide Assembly
The 270 Deluxe uses the traditional four-part sandwich construction consisting of the mouthpiece laid over the U-channel, a U-shaped housing that covers the top and slides of the slider, which rests on a backing plate that covers the front of the reed block (reedplates and comb). Newer designs usually try to reduce the number of layers, thereby reducing air leakage.
The 270 Deluxe slide measures at 0.67mm thick. Its channel measured at 0.93 before I disassembled it to photograph, giving a slide clearance of 0.26mm. However, after I reassembled the instrument the slide still moved freely with a clearance of only 0.1 mm.
|The 270 Deluxe has one new hidden feature—the ability to install the slide with the button facing left instead of right. This allows for left-handed operation of the slide or right-handed operation with the harp turned upside-down. To accomplish this, the slide hole in the front of the comb appears at both left and right ends, and the slide post—the metal post that anchors the slide spring—is provided for both sides as well.
|The injection-molded comb of the CX-12 Jazz has a front fence. This acts as a surface that can replace the backing plate. The shell portion of the mouthpiece acts as the U-Channel, eliminating another part. In the following photos you can see the comb fence covering the fronts of the reedplates (and the place where the slide attaches to the side of the comb), and you can see the slide housing in the shell.
The next photo shows how the slider and comb interlock. The hook at the bottom of the slide button limits the outward travel of the slider, while the spiral spring between the slide button and the comb provides tension and allows the slider to spring back.
The slide itself is completely enclosed inside the body of the harmonica and therefore far less vulnerable to damage (such as bending) than a slide on a standard harmonica.
The slide is 0.8mm thick. When laid in its channel inside the shell, it has a clearance of 0.1 mm.
The pearwood comb used in the original 270 remains nearly unchanged in the 270 Deluxe. Hohner mentions that it is partially sealed against moisture, but a close comparison with the regular 270 comb reveals no obvious differences in finish.
Custom builders have been retrofitting the 270 for screwed-together construction for decades. However, the Hohner solution has some advantages. Builders who used the Hohner comb had to place screws where they didn't interfere with the reed slots. At the long-slot end of the harp, this could be problematic, as the longest slots being only about 3mm from the back edge of the comb. Hohner has shortened the Hole 1 and 2 slots slightly to give more room to allow for the screw holes.
Of course a custom builder could make a new comb to allow for optimal screw placement without interfering with the slots. A number of customizers have made their own combs, but in most custom combs I've seen the reed chambers are flat-bottomed, probably because it's troublesome to duplicate the ramps that are built into all 270 combs. While the gentle concave downward curve of the 270 ramps appears to derive partly from convenience in wood milling, it has the advantage of reducing the amount of air required to fill the reed chamber, and to some extent can be tuned to favor the frequency of the note. Tuning the chamber by reducing its size is especially important for the highest notes, and the floors of Holes 11 and 12 are raised considerably in the 270 comb.
The CX-12 Jazz comb does not have the sloped ramps seen in the wooden 270 comb. The first four chambers are flat-bottomed, while flat ramps that raise the floor of the chamber begin in Hole 5, increasing in thickness through Hole 12.
Disassembly and Reassembly
The 270 Deluxe requires two different screwdrivers to disassemble. The cover screws and the mouthpiece screws require a straight-slot screwdriver (as does the original 270). However, the reedplate screws require a Philips or Pozidrive screwdriver. It would have been nice if Hohner had changed the cover and mouthpiece screws to match the drive used on the reedplate screws.
The cover nuts are still the annoying little flat nuts that are hard to grasp. I wish Hohner had used a nut more like the screw-head nuts used in the 64 series of chromatics. Likewise, the mouthpiece screws are wood screws that cut into the wood of the comb and they will eventually strip out the holes; installation of a nut to receive machine screws could have eliminated this problem.
The reedplates are fastened with seven screws (not five as stated in the spec sheet). All screws are along the back of the reedplate only; screws along the sides (as with the nails on the original 270) and/or front (as with the CX-12 and 270-inspired Hering models) could have made the instrument more airtight.
The CX-12 Jazz has no concerns with cover or mouthpiece fasteners, as the shell and reedblock are held together with a sliding tension bar that fastens to the back of the shell. To remove the reedblock, just disengage the slider hook, then slide out the tension bar. Recent versions of the tension bar have a gentler curve than older ones, making for easier sliding and less likelihood that the tension will break the shell. The slider is also easily removed and reinstalled.
The reedplates are fastened to the comb with 12 screws (not 11 as stated in the spec sheet), 7 at the back and 5 at the front of the comb. This provides an excellent seal but requires a lot of work to disassemble and reassemble when you need to work on inside reeds or valves.
My overall impression of both of these instruments is very positive. Assembly of parts, airtightness, tuning, and slide response were good on both instruments. However, on the instruments I received, I found that inconsistent gapping made some notes very hard to play without choking. Some valves, especially on the CX-12 Jazz, made loud flapping noises that interfered with notes being played, and some reeds, while gapped correctly, were jammed and would not play at all. I always avoid making any alteration to instruments under review, but in this case I could not record the instruments until I fixed these problems. As repairs go, they're minor ones, but a novice player with no repair experience would be helpless to deal with them. Admittedly, I played only one example of each model, and their condition may have not been representative of the overall state of quality control. I certainly hope not, because in every other way these instruments are a joy to play and to listen to.
The 270 Deluxe has a complex sound that the player can make dark or bright. Adjectives like smoky and even burning come to mind. Like all 270s it has a bit of air around the sound. This is something the player can utilize in soft and medium volume passages, but may have to work to overcome in louder passages. Response to soft playing in the top register is one of the tests of a responsive instrument, and I found the 270 Deluxe very good in that area. However, I would have liked a bit more tightness in the bottom register, although you can hear in some of the recorded examples that I was able to get plenty of fullness of sound in the bottom notes.
The CX-12 Jazz is immediately louder than the 270 Deluxe. It sounds like a CX-12, brighter and more “up-front” than the 270—the adjective that comes to mind is “fat,” with “sweet” not far behind. Some people really like that sound, while others prefer the classic sound of the 270. The notes seem more malleable—they bend easily, which requires some control if you're not used to it. I was able to get more volume and a wider dynamic range from soft to loud with the CX-12 Jazz than with the 20 Deluxe.
Comparative Recordings - Identical Passages
To compare these two harmonicas playing identical passages, I used the same tests and the same recording conditions as for the harmonicas reviewed in the October 2009 issue. I played each harmonica 4 inches (10 centimeters) from a Shure SM-58 microphone and recorded the results. I used the same input volume settings for all recordings, with an open hand cup. I did not use any equalization or compression, but did use a slight room ambience patch as the only effect.
C Major Scale comparison
On each instrument, I played the C major scale, ascending and descending, first softly, then at medium volume, then loudly, in the low, middle and top octaves.
To hear the 270 Deluxe play the scale, click here: 25-01
To hear the CX-12 Jazz play the scale, click here: 25-02
Long Tones Comparison
On each instrument, I played the note F, first as a draw note and then as a blow note, playing a long note that starts softly, swells to loud, then back to soft. I do it in the low octave, then the middle, and finally the high octave.
To hear long notes on the 270 Deluxe, click here: 25-03
To hear long notes on the CX-12 Jazz, click here: 25-04
Comparative Recordings - Improvised Melodies
Third position blues
Cupping the harp to an Audix Fireball V microphone, I play two verses of blues in D, using tongue-blocked chords, split intervals, and octaves. The first verse is played with no effects, the second with an effects patch that emulates amplifier distortion. As these performances are improvised, I do not attempt to play the same things literally on each instrument. Rather I let the qualities of the instrument guide me.
To hear the 270 Deluxe playing third position blues, click here: 25-05
To hear the CX-12 Jazz playing third position blues, click here: 25-06
Playing into an SM-58 microphone left on a stand to allow for hand cupping, I improvise over a backing track in the key of E major (from my original song “Cup of Wine”), again letting each instrument guide my improvisation.
To hear the 270 Deluxe playing in E major, click here: 25-07
To hear the CX-12 Jazz playing in E major, click here: 25-08
The upgrades built into the 270 Deluxe make it well worth the price difference between this model and the regular 270, and it has been well received in the community of players who prefer the sound and playing response of a 270-type instrument (Dennis Gruenling, who loves the 270 Deluxe, is hoping for a 16-hole “280 Deluxe” reminiscent of the prewar, straight-tuned, wood bodied Model 280). I only hope that that the 270 deluxe will be offered in more keys in the future.
The CX-12 Jazz is a fine instrument with a distinctive sound and playing response. The reshaped mouthpiece of the shell will offer greater embouchure comfort to many players—you can hear how fluidly I could play octaves in the blues example. However, the additional value of the altered mouthpiece simply cannot justify the whopping price difference over the regular CX-12, which itself offers good value for the money. Hohner Germany may want to reconsider its pricing strategy if they wish to make this model sell well.
Recommended Book—Basic Blues Chromatic
Please visit http://www.harmonicasessions.com/feb05/ChromaticTab.pdf for a notation key.