Keep that Slider Slidin’- Part 1
Chromatic for Diatonic Players
By Winslow Yerxa
The slide mechanism is what separates the chromatic from other types of harmonica. Of course, not every chromatic player takes full advantage of it. Witness the famous photograph of blues harmonica icon Little Walter Jacobs holding a Hohner 64 with the slide button broken off. Or listen in on a harmonica club playing session where everyone plays a tune in C, then presses the slide button and holds it in to repeat the tune in C#, just for some variety.
But many players (even Little Walter, despite that photo) use the button actively, moving it in and out constantly as we play. But the slide assembly can cause several problems—it can make unwanted noises, leak air, freeze in place, get sticky and sluggish, and grate. The slide button can fall off, the return spring can break, and the slide is vulnerable to being bent, making it impossible to move.
What to do about these annoying problems? And how can you make your slide work better in general? Over the next few issues, I’ll touch on ways to deal with these problems and improve slide performance.
But first, an overview of the mouthpiece/slide assembly.
Anatomy of a Sandwich
A chromatic harmonica has two banks of reeds tuned to two different keys a semitone apart, such as C and C#. The slide is a flat strip of metal with holes punched in a pattern so that only one bank of reeds will sound at a time. On a chromatic tuned to the key of C, when the slide is at rest, you can play the notes of the C Major scale. If you press on the slide button at the left side of the harmonica, the slide shifts so that the holes leading to the bank of reeds for the C scale are covered up, and instead air is directed to the bank of reeds that play the C# scale. Between these two banks of reeds, you can play all the notes in any key.
The picture shows a chromatic harmonica (It’s a Hohner Super 64x), with the mouthpiece visible, and the slide button sticking out at the right side. Look into each hole and notice how either the top or the bottom half of the hole is blocked off.
The slide is the only moving part in a stack consisting of anywhere from two to four layers. The mouthpiece is the outermost layer. It gives you a comfortable surface to put in your mouth, simplifies air direction by consolidating two holes in the harmonica into one, and keeps your lips and tongue away from the slicing action of the slide. The shape of the mouthpiece and the holes are major elements in comfort, and I’ve given these a lot of attention in the reviews of individual harmonica models in past issues.
The mouthpiece screws, visible in Figure 35-1, bind the entire assembly together, starting with the mouthpiece and going through all the layers and into the body of the harmonica. Together, the screws and mouthpiece are what tighten the assembly by pressing on the lower layers. What lies beneath the mouthpiece depends on whether the mouthpiece/slide assembly has two, three or four parts. Four-part assemblies are the most traditional, so let’s start with those.
In four-part assemblies you have:
- The Mouthpiece – The mouthpiece rests atop the slide cage.
- The Slide Cage or U-Channel – This layer, which resembles an inverted, flat-bottomed U, gives the slide a channel to move in. The main surface of the U-Channel is above the slide, while the sides reach down past the slide to meet with the backing plate.
- The Slide – This is a flat, sliding grid with rectangular holes along its length and a finger button on its left end. The slide is the heart of the action, directing air to one bank of reeds when it’s in the out position, and another bank of reeds (usually tuned one semitone higher) when pressed in. An attached spring lets the slide spring back to the out position as soon as you release pressure from the button.
- The Backing Plate – This thin, flat metal plate full of rectangular holes gives the slide a consistent, flat surface on which to glide. Backing plates are needed in harmonicas with combs milled out of blocks of wood, metal, or plastic, as the sandwiched layers of top reedplate, comb and bottom reedplate do not provide a sufficiently uniform surface.
You can see a four-part assembly of a Bends Tonica chromatic in profile in the picture below. The rightmost part is the mouthpiece, with the surface of the U-Channel, then the slit where the slide is located, then the backing plate covering the comb (clear plastic) and the reedplates (brass). This picture is taken from the opposite end of the harmonica from where the slide sticks out, to show a clearer view of the U-channel and backing plate.
The following photo shows the parts of the assembly from a Hering Stan Harper disassembled and laid out. At the top is the comb, followed by the backing plate, slide, back of the U-Channel, and back of the mouthpiece.
Note the slide spring sticking out of the hole drilled in the comb at right. This is inserted in the tiny hole in the slide, visible near the slide button.
Also note the short length of plastic tubing jutting up from the hole near the right end of the U-Channel. That’s known as a bumper. It wraps around the mouthpiece screw and prevents the slide from hitting the screw, thus avoiding unwanted noise and protecting the slide and the screw thread from each other.
Harmonicas that use four-part assemblies include all Bends and Hering models, all Huang models, Seydel Standard and Deluxe models and Suzuki Leghorn. Hohner models that use four-part assemblies include the 260 Chromonica, Slide Harp, Koch 980, 270 Super Chromonica, 12-hole Larry Adler model, Toots Mellow Tone and Toots Hard Bopper, and the earliest versions of the 16-hole models (roughly pre-1955) such as the Model 280, Chromonika III and 16-hole Larry Adler model. Sometime in the mid-1950s these models were converted to a three-piece assembly.
The Seydel Saxony and Saxony Orchestra sport a unique version of the four-part assembly, in which the backing plate is replaced by an I-beam. One side of the I-beam clamps the front edges of the reedplates to the comb while the other provides a U-Channel for the slide, which is topped by a front plate that rides the rails of the I-beam and provides a platform for the mouthpiece. The picture below shows a progressive build-up of layers in a Saxony mouthpiece assembly.
In most three-part assemblies, the U-Channel is integrated into the back of the mouthpiece, thereby eliminating one of the layers, simplifying construction, and reducing leakage.
You can see the three-part construction of the Hohner Meisterklasse in profile in Figure 35-5. The backing plate stands out due to the brass color. Note how the slide channel is formed by the back of the mouthpiece.
The picture below shows the Meisterklasse three-part construction with the parts laid out, with the backing plate at top, followed by the slide and the back of the mouthpiece.
Harmonicas that use three-part construction include the modern versions of the Hohner 280 and the 16-hole Larry Adler model, the Super 64 and Super 64x, the Meisterklasse, the Suzuki SCT-128 tremolo chromatic and the Fabulous models.
In some harmonicas, three-part assembly can be simplified even further. The injection-molded plastic combs of the Hohner 16-hole chromatics have a feature that is not shared by combs milled from a solid block: the front fence. Instead of having the front edges of the reedplates meet the front face of the comb, a vertical face is added to the front of the comb that recesses the reedplates and provides a smooth, consistent surface for the metal backing plate. The picture below shows the front fence of the plastic comb standing in front of the reedplates of a Hohner CX-12.
At some point, harmonica customizers realized that the fence itself would make a good backing plate, and started removing the backing, eliminating another layer and potential source of leakage. And now the number of layers in the mouthpiece/slide assembly was reduced to as well.
The first production harmonica to use a two-part assembly was the Hohner CX-12, where the outer shell integrates both mouthpiece and U-channel, and the front fence provides the backing plate. The CX-12 is famed for its airtightness, and this simplified construction is one of the reasons. You can see the slide channel inside the CX-12 shell in picture below.
In recent years, Suzuki has also eliminated the backing plate from its plastic-combed harmonicas, including the SCX, G-48 and Sirius models.
In the late 1950s, Hohner brought out a line of inexpensive student chromatics, called the Chrometta. The design was revolutionary for its time, and it reduced the slide assembly to one piece: the slide. The mouthpiece is part of the comb, and the slide is inserted into a slit between the mouthpiece and the hole dividers, as shown in the picture below.
While this construction is the ultimate in simplicity, it has one flaw—there’s no way to tighten the space around the slide to eliminate leakage.
You’ve now seen the major mouthpiece/slide assemblies. We haven’t discussed springs or the difference between cross and straight tuning, but we’ll get to that next time, and then dive into ways to fix problems and then how to improve your instrument’s slide airtightness and action.