An original flier from a 1950s Kay Archtop with the Kanti-Lever truss rod system

I went ahead and transcribed the letter for your reading pleasure.

HOW TO USE YOUR "KANTI LEVER" ADJUSTABLE GUITAR NECK

Your new guitar is equipped with a balanced tension neck. The purpose of this adjustable feature is to enable you to keep your guitar neck in perfect alignment at all times.

Having been made very thin to permit fast, tricky progressions, the wooden neck is subject to atmospheric conditions. These atmospheric conditions, plus the tension of the strings, tend to warp or bent the necks. In addition, the alignment of the neck is affected by a change in pitch, change of strings, and a change of bridge height. You can now keep your neck in perfect alignment with Kay's ingenious "Kanti Lever" reinforcement inside the neck. Built around the lever principle, with a specially alloyed steel truss rod and a positive screw adjustment, this neck is now virtually fool-proof.

Your guitar neck was perfectly aligned when it left the factory. Should any further adjustment be needed, you can do it yourself with the handy "T" wrench that was included. Insert the wrench in the hole in the heel of the neck (where the neck joins the body) turn the key to the right (clockwise) to adjust the neck back; turn the key to the left (counter-clockwise) to bring the neck forward. Ordinarily, a turn or less will put your instrument back in perfect alignment. Do not readjust the neck unless it proves necessary. Be sure your guitar is in tune before readjusting the neck.

Dating Harmony Guitars

Harmony guitars are fairly easy to identify and date yet there still remains a lot of unsolved questions for the average collector which I am attempting to answer here.

The single best resource on the internet is the DeMont Harmony Database but it is no longer updated.

I am attempting to bridge the gap where he stopped and with what we know today.

I cite my information as best as I can but there are points that are common knowledge among the Harmony community or are observations and conclusions that I have reached from my work.

Pictures are mine unless otherwise cited.

If you are unable to identify your instrument, use the Contact Me button above and I'll do my best.

1914 Advertisement for Harmony
Image Credit

Branding

Harmony instruments have their name on them more often than Kay instruments do but there is still a significant number of these instruments which do not sport the name of the manufacturer. Many Harmony instruments have a brand name which was given by a retailer who purchased the instrument for sale as a house brand in their own shop. You can find Harmony guitars branded Airline to Heathkit to Wizard and more!

I have assembled a master list of brand names and who built for them 
Department Store Guitar Brand List

Company History

1892

• William J. F. Schultz forms the Harmony Company with a capital stock of $25,000
• Employed four workers [2]

1904

• Harmony Co establishes their factory at 1750 N. Lawndale Avenue [2]

1916

• Sears-Roebuck & Co purchases The Harmony Company [3]

1917

• Capital stock increased to $100,000
• Employed 125 people
• 70,000 instruments were being produced per year [2]

1940

• Under talks of unionization, Sears-Roebuck sells the Harmony Company to former Harmony president Jay Kraus and work ceases on December 21st, 1940 [3]

1941

• The Harmony Company spends 6 months moving to 3631-3633 South Racine Avenue 

1954

• Harmony purchases the trademarks and brands of the defunct Regal Musical Instrument Company [1]
• Regal guitars were sold exclusively through Fender Sales Inc 

1962

• The Harmony Company moves to 4600 S. Kolin Ave [2]

1977

• The Harmony Company is liquidated and all of the tools, materials, in-progress instruments, and trademarks were sold at auction

Headstock Variants

Quintessential Harmony headstock shape
[1936-19??]

Slender-waist
[1930s]

Thin, small nub
[1940s]

Kay-esque single point
[Late 1960s-1970s]

Tuning Machines

Harmony guitars primarily used Waverly tuning machines on their models throughout the lifetime of the company. Kluson tuners started appearing in the 1940s.

My guide to identifying Kluson tuners can be found here
My guide to identifying Waverly tuners can be found here

Bodies

Harmony acoustic instruments are praised for their use of solid woods. They require more care than laminate guitars (to prevent cracking) but provide better tone.

Carved vs Pressed

Most Harmony archtop guitars have heat pressed tops which are formed in molds to make the archtop shape which produces a good sound but is nowhere near as desirable as a true carved top. 

There do exist models where the bracing is carved out of the same piece of wood as the top.

Necks 

• Poplar is the most common wood used 
• Often finished in a brown lacquer to mimic mahogany
• Mahogany 
• Appears on higher end flat top models like the Sovereign series 
• Also appears on mid to high end archtops as early as the 1940s. 

Neck Reinforcements

Double bar reinforcement slots on a 30s archtop

• Pre-1940s - Single or double rectangular steel bar
• 1940s - Often none
• 1950s-1970s - Single rectangular steel bar

Truss Rods

Harmony unveiled the Torque-Lok dual-rod truss rod system in 1956 which was paired with their Slim-Line neck for 'professional' and 'fast' playing.

Unfortunately the design has flaws. As tension is added to the rod, the nut is forced downwards into the channel but the upward pressure which makes adjustment difficult. The rod also stops short of spanning the full length of the neck which reduces its, already weak, effectiveness.

1950s Harmony "Torque-Lok" Truss Rod
Partially removed for demonstration

Fretboard

• Brazilian Rosewood
• Continued to appear on mid to high-end models far into the 1960s
• Ebonized hardwood (maple, birch, etc)
• (Read my Article here about the process)
• Very common on low-end models throughout Harmony's history
• Ebonizing process causes the wood to 'dry rot' which reduces its strength and leaves it brittle and prone to cracks and chips.
• Very unpleasant to refret. 
• Indian Rosewood
• Started appearing in the 1960s as a cheaper alternative to Brazilian
• More porous and differently colored than Brazilian Rosewood 

Position dots

Inlay materials are typically real pearl up until the 50s when celluloid "pearloid" becomes commonplace.

• 3/16" white dots in an alternating 1 and 2 dot pattern appeared in the 1930s
• Kay also used this pattern and dot size
• Ornate stenciled designs can also be found
• Painted on, typically, with white lacquer

Frets

• Composition
• Standard nickel frets are the most common
• Brass frets appeared in the 1940s
• Size
• Thin, short frets were common before and during WWII
• I cover a variety of exact fretwire dimensions on my article Vintage Fretwire Dimensions

Stamps

Harmony guitars are, in most cases, very easy to identify via their comprehensive stamping and dating system. Ink stamps are typically found on the back of the instrument and are visible through the f holes or soundhole. It is not uncommon for the stamps to be poorly inked, faded, or obscured.

Harmony date stamps variants
Image Credit: UNKNOWN
Please contact me if you made this so I can applaud you

• "F-##", "S-##"
• Means Fall or Spring which refers to the season in which the instrument was built
• It does not mean First or Second half of the year
• The existence of "FL" date stamps and of Christmas-exclusive models bearing "F" stamps (for Fall) supports this conclusion
• "##" refers to the year in which the instrument was built
• If followed by a letter or letters, that indicates the inspector of the instrument that approved it. 

Harmony H-54 built in the Fall of 1951
"3585" has no known meaning and can be ignored
Image Credit: Ebay

• "####H####"
• Preceding numbers are likely a batch number and have no discernible meaning
• Following numbers are the model number of the instrument and can be easily researched on such websites as the DeMont Harmony Database
• Harmony was known to reuse model numbers

• "Carved Top"
• Often printed in red ink, indicates a high end model with a carved arch top

1938 Carved Top Stamp
Image Credit: Reverb - Tommy

• Dovetail Stamps
• Sometimes the dovetails will have stamps on the heel that can only be seen during a neck reset
• Possibly another method of dating the instrument? I'll have to find more examples

4847 stamp on dovetail on a 1948 archtop

• Miscellaneous Stamps 
• "PVC"
• Unknown meaning

From a 1940s "Gene Autry"

• "UV-S2S"
• Unknown meaning

From a 1940s Harmony Monterey

Labels

Harmony guitars typically don't have any paper labels glued inside them from the factory. Most paper labels are from the distributor like B&J which had their own serial and model number labels. Starting in the 1960s, select models had labels which were visible through the soundhole or f-holes.

• "A Quality instrument handcrafted by The Harmony Company"
• Appears on 70s Harmony guitars, a few USA but mostly Korean built
• "Special Notice This guitar is designed for nylon or gut strings do not use steel strings"
• Appears on 60s-70s classical guitars warning players not to use regular acoustic strings

Pickups

Harmony purchased their pickups from outside suppliers and, to my knowledge, did not wind their own.

DeArmond-Rowe

Harmony pickups were built primarily by DeArmond-Rowe Industries which constructed the famous "hershey bar" and "gold foil" pickups (not to be confused with later Japanese gold foil pickups). If your Harmony has electronics, chances are that they are DeArmond. DeArmond also assembled the wiring harnesses for pickguards that used their pickups

Luckily, DeArmond units are well documented and typically have a date stamp on the back of the instrument in Month Day Year format like MAR 18 1966. This will align very closely with the date of construction of your instrument. The best resource for DeArmond pickups is https://www.musicpickups.com/

Gibson

Gibson P-13 pickups are often referred to as the precursor to the famous P-90 pickup and were built in the 1940s and 1950s. There is a rumor that Gibson sold Harmony a "boxcar" of pickups and Harmony used that stock until they ran out. Nobody knows the specifics but we do know for sure that Harmony used Gibson pickups (and Gibson lap steel wiring harnesses) in some of their instruments.

1950s Gibson P-13 Pickup (no polepieces) on an H-56 Roy Smeck

Do not confuse these pickups with Speed Bump pickups from Kay or pickups from Alamo. Too many people falsely attribute these pickups to each other but they are not associated in any way except appearance

Common Issues 

DIY repairs are the quickest way to damage and devalue an instrument

Always consult with a reputable luthier (not a guitar tech) before performing any work

Never ever use super glue, epoxy, gorilla glue, or Titebond III

Guitars that are 'repaired' with these are often beyond saving

• There are cracks in the wood
• This occurs when an instrument is exposed to a climate different than the ideal (70 degrees Fahrenheit and 45-50% humidity) and the wood has shrunk
• Do not try to fill the cracks with glue or put clamps on the guitar to press it together
• Your guitar needs proper humidity and cleats
• The neck heel is pulling away from the body
• Do not shove glue in there or drive a screw through the heel
• Your guitar needs a neck reset 
• The frets have large divots in them
• Frets are like tires on your car, they need replacing after being used a lot
• Your guitar needs a refret
• The strings are buzzy or the neck is bowed
• Most Harmony guitars lack adjustable truss rods (or rods that still work) and so forward bow cannot be easily repaired.
• Your guitar needs a fretboard planing and refret or more ideally a truss rod installation
• The strings are too high off the fretboard
• As string tension and climate shift the wood in a guitar, they inevitably need the neck to be steamed off and a new angle carved relative to the body.
• Your guitar needs a neck reset
• The bridge is lifting and coming off
• Many bridges are glued directly onto the lacquer which causes them to lift and raise the action. 
• Do not use glue to fill the gaps or drive screws into the bridge to bring it back down. The only fix is to remove the bridge, prep the area, sand the bridge to match, and reglue it.
• Your guitar needs a bridge reglue and often a bridge plate patch
• There is no sound coming from the electronics
• This can be a variety of things from dead capacitors, dirty potentiometers, shorted wires, and even dead pickups.
• Don't replace any vintage components unless you absolutely have to
• Your guitar needs an electronics evaluation and cleaning

Sources

[1] https://www.snathanieladams.com/2021/09/regal-musical-instrument-company.html

[2] https://www.madeinchicagomuseum.com/single-post/harmony-company/

[3] https://www.snathanieladams.com/2022/02/melody-instrument-company.html