This Storytone piano by is one of only 150 made and was the world's first electric piano model. It debuted at the 1939 World's Fair and the early models had DeArmond tremolo units mounted under the keyboard. Photo by Dave Fey

Early Electric Guitar Tremolo
By 1941 the DeArmond company had developed what may have been the first effect unit for guitarists. It resides between the guitar and the amplifier like today’s effects. Inside the metal box is a small glass jar containing a water-based electrolytic fluid, which gets shaken by a motor. Inside the jar is a pin attached to the positive connection of the guitar cable. As liquid splashes against the pin, signal is shunted to ground. The result: great-sounding, liquid-like tremolo.

The 1941 date is not based on the effect being used with guitars, but on the first electric pianos. Storytone pianos were manufactured by Story & Clark and developed in conjunction with RCA. They were first exhibited at the 1939 New York World’s Fair. By 1941 early models boasted DeArmond tremolo units mounted directly under the keyboard for easy access. In August of that year, pianists J. Russel Robinson and Teddy Hale performed at the Chicagoland Music Festival, their state-of-the-art Storytones outfitted with both DeArmond units and Hammond Solovoxes (miniature, secondary keyboards, and some of the first synthesizers.)

Andrew Appel’s patent for an early electronic tremolo device.

There wasn’t much musical instrument development during World War II, so the second effects box may have been Andrew Appel’s 1945 tremolo device. His design, housed in a metal box quite similar in shape to the DeArmond unit, arranged resistors in a circular pattern in ascending order of resistance. A motor rotated a contact that successively touched each resistor. The result, in theory, was equivalent to quickly raising and lowering your guitar’s volume control. Again, even though the effect only changed volume, Appel described the device as creating “tremolo or vibrato effects in conjunction with an electric type stringed musical instrument.” (Note: I have never seen this unit and am not sure if it ever went into production. If anyone has further knowledge, please let us know!)

Other mechanical innovations? Donald Leslie first attempted to patent a rotating horn device in 1940. (He abandoned that first version, but followed up in 1945 with an alternative.) His earliest design incorporated a stationary speaker that faced upward, its sound flowing into the small end of a rotating horn a bit like the ones on early Victrolas. His patent describes the effect as producing “pitch tremolo or vibrato.” The rotating horn or speaker in the classic Leslie cabinet produces tremolo and vibrato simultaneously. As the speaker or cone moves towards you, the sound waves move faster, slightly raising pitch. The pitch lowers slightly as the speaker moves away. Meanwhile, volume is greatest when the speaker faces you. Therefore “tremolo and vibrato” is an accurate description of the Leslie effect.

The First Guitar Amp Tremolo
Nathan Daniel created the first guitar amplifier with vibrato in 1947, the year he founded the Danelectro company. He called it a “Vibrato System for Amplifiers,” and his extended description explains that the circuit produces a “tremolo or vibrato effect.”

The Premier “66” may have been the first amp introduced with tremolo, in 1947. Gibson’s GA-50T from 1948 was one of the first amps to feature a built-in tremolo effect. Fender’s first tremolo amp was 1955’s Tremolux. Later brownface and blackface Fender amps would feature radically different versions of the effect.

The patent was granted in 1949, but we’re not sure exactly when the circuit was first used in a Danelectro amp. According to Nathan Daniel’s son Howard, “I have no knowledge of this, and I suspect there's no living person who does. I can speculate, however, based on my knowledge of my dad, that he introduced tremolo sooner than 1950, as soon as he could following his application for a patent.” Tremolo definitely appears on Danelectro’s 1950s Special model amps.

But Multivox and Gibson may have beaten Danelectro to the market with trem-equipped amps. A 1947 Multivox ad trumpets the company’s new model: “Guitarists! You owe it to yourself to try the new Premier ‘66’ Tremolo Amplifier. Yes, you too will be sold on this new amplifier from the very first trial. The built-in Electronic Tremolo lends a new organlike quality to your tone.” Meanwhile, Gibson’s first tremolo amp, the GA-50T, appeared in 1948.

(Note to Magnate fans: While Magnatone began manufacturing steel guitar amps in the late 1930s, their first tremolo-enabled amplifier, the Vibra-Amp, didn’t arrive until 1955. Their “true vibrato” circuits, using varistors to alter pitch rather than volume, first appeared in 1957’s Custom 200 series.)

The tremolo section of a vintage amp circuit (yes, it’s called “vibrato” on many amps and schematics) involves at least one tube. A wavering voltage affects the tube’s bias. How that wavering voltage is generated, and to which section of the amp circuit it is applied, account for the sonic differences between various tube tremolo circuits. Without getting too technical, let’s look at how they work, using several Fender tremolo amps as examples.

Fender’s earliest tremolo amplifier appeared in 1955, relatively late in the game. The tremolo section in a ’55 Tremolux amp uses a 12AX7 tube, resistors, and capacitors to vary the voltage. All amps with two or more power tubes include a tube called a phase inverter, which splits the guitar signal to allow two (or four) power tubes to share amplification duties. The Tremolux is unique in that the wavering voltage is sent to the cathode element of the phase inverter.