Hammond Solovox Tone Cabinet (1948)
The Hammond Solovox is a pioneering electronic keyboard instrument,
dating from the 1940s and manufactured by the Hammond Corporation,
famous for their organs. It was created by Laurens Hammond, the
company founder, and engineers John Hanert and George Stephens.
Much of the following article was written thirteen years before I
acquired another, similar 1940s electronic instrument, a Gibson
The following photos picture the two instruments separately, with
the Solovox on the left:
My Clavioline is a very recent (Fall, 2011) acquisition. When I get a little
more time, I'll compare their performance and perhaps have more to add to
both of their articles.
Finding a Solovox
When I spied a mysterious cabinet with a speaker at a thrift store, I was
immediately intrigued. The brass plate on the back declared it
to be a Hammond Tone Cabinet. Now, Hammond was a
big manufacturer of tube-powered organs, but if
this is a musical instrument of some kind, where's the
If you have ever peeked inside a tube organ,
you know that it will have many more tubes than the
thirteen seen in the back of this device. With so
few tubes, what kind of music could this critter make—if
it generates music at all?
Pondering for a moment, I decided that the tubes
alone were worth more than the asking price, so,
partly out of curiosity and partly to save it from a worse
fate, I handed over the cash and hauled it home.
The mystery was quickly solved when I posted a query to the rec.audio.tubes newsgroup on USENET.
One of these followed me home, and now I'm curious.
This is a knee-high wooden cabinet, very shallow, with
13 tubes and a decent-sized speaker inside, and a big
flat sixteen-pin connector on the end of a cloth-covered cable.
The cabinet has a flat back and rounded edges -- perhaps
it was meant to stand against one end of an organ. A brass
plate identifies it as a Model L tone cabinet, to be used with
a Model A keyboard.
Anybody familiar with this mystery device?
This reply came from Thomas Lehman:
This is a Hammond Solovox cabinet. The part you are
missing is the little keyboard that attached to the front of
your regular piano keys. It allowed you to play single note
organ solos while you played the piano. The keyboard had
voice controls and a leg operated volume lever.
This patent drawing shows the Solovox keyboard, mounted on a piano:
All very interesting, but without a keyboard, the Solovox can't make any music!
I owned the silent tone cabinet for about two years before I found
a keyboard for sale. The seller owned a complete Solovox but he wanted to use
his tone cabinet for another purpose. After we had made a deal for the keyboard
alone, he abandoned that scheme and offered me the tone cabinet for an additional $15.
I didn't particularly want two cabinets, but I decided to buy his
complete Solovox, including keyboard, and that's the one which I restored:
I later sold the first cabinet to another collector who had nothing but a keyboard.
The next photo shows my new keyboard, mounted to the workbench.
From left to right, the control buttons are labeled Bass, Tenor, Contralto, Soprano,
Mute, Fast Attack, Vibrato, Deep Tone, Full Tone, First Voice, Second Voice, and Brilliant.
You can learn more about these controls, and Solovox playing in general, from the Owner's
Manual provided later in this article.
Restoring the Hammond Solovox
Restoring my Solovox was not difficult. Although its purpose
is quite different, the Solovox's internals are not much different from what
you'll find inside a typical tube radio: tubes, resistors,
paper capacitors, and a few coils.
The keyboard, of course, has no counterpart in the radio world. It is complex,
with delicate switch contacts and a number of coils and resistors inside.
Unless a keyboard has been damaged, however, it should only
require some cleaning.
My new tone cabinet worked, but its sound was rather weak and the vibrato
didn't work at all.
My first step was to open the keyboard and clean the switch contacts with
DeOxit. It's not necessary to completely disassemble the keyboard; as this
diagram suggests, it's not a simple mechanism.
I also cleaned the volume control and four additional controls located under the keyboard.
Those four controls are used to tune the keyboard to your piano and regulate
the minimum and maximum volume.
Another important step for every old tube device is to remove every
tube and clean its pins. If you do this one tube at a time, you won't
accidentally switch two of them around. While each tube was out, I also
checked it on my tube tester, to cull any weaklings (there weren't any).
Next, I removed the chassis and speaker from the tone cabinet.
Here is the chassis on my workbench, ready for restoration.
The tan tubular components are old wax paper capacitors. I replaced
them all with modern ones. My capacitor replacement
article explains that process for those who aren't familiar with recapping.
When I was done, the tone was much stronger, the various voices
were distinguishable, and the vibrato worked again. The vibrato
was harsh, however, creating almost an on/off effect rather than a soft
variation of pitch. I remedied this by replacing a resistor connected
to the vibrato oscillator tube. As with some old resistors, its value
had "drifted" with age beyond normal tolerance.
After restoring the electronics, I restained the cabinet to blend away a few
scratches. Then I reassembled everything and mounted
the keyboard under my workbench:
As you can see, new "orange drop" capacitors have replaced
the old paper caps on the chassis.
Here is a photo of my younger son, Peter, trying out our freshly restored Solovox
in the late 1990s:
A single-voiced instrument can't play chords, of course, but the Solovox
can create a surprising variety of sounds. And, as Peter told me,
you can use techniques such as arpeggios for
In 2011, while home on a break from music school in Boston, Peter obliged me by
recording a brief audio sample on the Solovox. Click the musical icon to hear it:
Solovox Schematics and Manuals
When I bought my Solovox, the deal included the original owner's manual and technical
manual, both dating from 1948. I also have run across a couple of magazine articles
which include schematic diagrams and technical information about the various models
of Solovox (J, K, and L). The total documentation amounts to about 50 pages.
You can download this documentation from the following links. These
are rather large files—a few megabytes each—and they are in
.PDF format. To save a file on your computer, right-click on the link and choose Save Target As.
The Solovox Owner's Manual
tells you how to install and use the Solovox, including settings for register (voice), tone, vibrato, attack, and so on. There are charts showing 77 different settings for
orchestral instruments, church organ, and other interesting combinations. It also includes some music written for the Solovox.
The Solovox Technical Manual
explains theory of operation and includes a schematic diagram, parts layout diagrams, voltage charts, etc., for Model L.
The Solovox Magazine Articles
are from Radio Craft, November, 1940, and Radio & Television News, December, 1948. Written for electronic dealers and technicians of the time, they provide additional
technical details, including schematics for models J and K.
Note that different Solovox models are not interchangeable. If you
have a keyboard from one model and a tone cabinet from
another, they will not work together without extensive modification (which is well beyond my talents).
If you are not able to download the documentation, just send me
an email with your mailing address.
The charge for the Solovox documentation is US$5 to cover the cost of photocopying and postage.
Thanks to Nils Sundquist of Eskilstuna, Sweden, for creating these
electronic files for me to share with other Solovox owners.
Solovox Repair Article
More than 10 years after writing this article, I ran across a 1949
issue of Radio Electronics magazine that features an article
about repairing the Solovox. Click on the icon below to read
Written when Solovoxes were still fairly new, the article
deals with a range of problems that might be found in any Solovox. Nowadays,
sixty-odd years later, every Solovox will have additional problems due
to aging, primarily aged capacitors and dirty or oxidized switch contacts.
In 2011, I got email from Wilfred Høsteland, a Hammond historian in
Bergen, Norway. He advised me that the Solovox was designed by John M. Hanert
and the tone cabinet was designed by Laurens Hammond himself.
Wilfred provided this additional information:
The Solovox was introduced in 1940 (model J) which had a
mechanical vibrato device. Then the model K came (1946), and
finally model L (1948). The main differences were in the number
and types of vacuum-tubes in the tone cabinet. It was said
that the Solovox was taken out of production in 1950, but it
was still advertised in the Hammond Times until October 1953.
(The two last versions had electronic vibrato.)
There was also a "military" version, self-contained with speaker
and keyboard in the same cabinet, for officer clubs, etc.
And, the Solovox was made in different colors: black, white
and mother-of-pearl. The last two versions were made mostly
on special order from famous organists, such as Milt Herth,
who wanted to use it with their Hammond organs. A number of
Hammond recording artists, such as Lenny Dee, also used the
Solovox as a special effect.
The Solovox also was the basis for other Hammond products
like the Chord organ S-series from 1950, the Extravoice organ
(introduced in 1959), and the pedal-solo system in the RT and
D-100 concert organ series.
Wilfred's email inspired me to a little more research, which turned up
three interesting Solovox patents.
covers the Solovox keyboard design and it was granted in 1941. It lists
Laurens Hammond and George H. Stephens as the inventors.
Design Patent 124405
was issued to Laurens Hammond in 1940 for his design of the Solovox tone cabinet.
Patent 2233258 describes
the electronics in the Solovox tone cabinet. Granted in 1941, it lists John
M. Hanert and Laurens Hammond as the inventors.
Notes from Solovox Owners
Since originally posting this article over a decade ago, I have
gotten hundreds of emails from Solovox owners, from as far away as Denmark and Japan. Some of these are pretty interesting.
For example, did you know that there was a Solovox songbook? Here is a
Solovox Album, complied and arranged by John Finke, Jr. for
Theodore Presser Co. of Philadelphia. It has a copyright
date of 1941. It is subtitled: A Collection of Special
Arrangements of the World's Best Loved Melodies for the
Hammond Solovox. It contains 32 tunes, including Arkansas
Traveler, Oh! Susanna, Old Folks at Home, Turkey in the
Straw, Home On the Range and Auld Lang Syne.
I have never seen that book, but it sounds like a lot of fun.
The following note indicates that the Solovox is
alive and well in polka circles:
I am a accordionist and have had a polka band for 22 years.
My first introduction to the Solovox came from America's
Polka King and First Polka Grammy winner, Frank Yankovic.
Frank had Solovoxes in his band in the late 1940s when they
first came on the market and Frank had two of them in the
band until the 1960s when he went to the Casio M-10 keyboard.
Many albums Frank recorded for Columbia records had the
Solovoxes in use. Frank and his piano player in the band
harmonized with two Solovoxes. Anyway, I have always wanted
one and yesterday I got one from a oldtimer here. He gave me
the Solovox that he bought in 1968 and used in his band.
In 2001, this email arrived from Hamburg, Germany:
Hello! This is Jurgen Lamke from Hamburg in Germany. I am a
pianist and organist for North German Radio (NDR). In our
broadcasting house we have a fine old "Welte-Funkorgel," a
theatre pipe-organ. In the 1950s, the organist Gerhard Gregor
installed a Hammond Solovox at this console. We still have
this Solovox and I would like to repair it for further use.
I am very interested in the documentation which you offer
In exchange for the documentation, Jurgen sent me two CDs featuring
Gerhard Gregor playing the Welte-Funkorgel in the 1960s and
This note arrived in 2003:
While helping clean out the basement of an old house, my
son found a Hammond Solovox keyboard. He was told he could
keep it, as the house was to be sold and had to be emptied.
It looked pretty darn weird to us, never having seen or
heard of one. The neat thing is that the vintage lettering
on front said "Pee Wee King!" He was in the Country Music
Hall of Fame and co-wrote "Tennessee Waltz" and many
other well known songs.
Here's another trivia note about the use of a Solovox in
If you knew "Sugar Shack" and "Daisy Petal Pickin'" by Jimmy
Gilmer and the Fireballs, you may have noticed there was a
Solovox in both of those songs. Norman Petty, who was also a
producer for Buddy Holly and the Crickets, did that part.
I have received many other emails from people who either owned a Solovox
or had a family member who played one in a band. Keep
those cards and letters comin', folks!