The 1956 Vibrolux operates on the same basic principle, varying the bias. It also uses resistors and capacitors, enlisting only half of a 12AX7. (A single 12AX7 tube houses two separate triode tubes, which can be used independently.) The modulating voltage enters the guitar signal path after the phase inverter, acting on the grid elements of the two 6V6 power tubes.

(The brownface amps Fender introduced in 1959—the Vibrasonic, Concert, and eventually other models—utilize a circuit called “harmonic vibrato.” It’s not exactly tremolo or vibrato, although it can certainly create that impression. Think of tremolo volume as a sine wave, with high and low peaks. Now think of a second tremolo wave, this time offset by 180 degrees. It would cancel the first tremolo—the summed volume would be flat. However, the harmonic vibrato circuits send higher frequencies to one wave and lower frequencies to the other. There is no actual change in volume or pitch, but rather a sort of phase shift.)

Fender’s next type of tremolo featured a very different system. The blackface amps that appeared in 1963 use a 12AX7 tube and a photocell to oscillate the voltage. That system employs a neon light to open and close the photocell. It acts on the grid of the phase inverter. Photocell tremolo tends to sound choppier than earlier bias variation circuits. (For an example of bias variation tremolo, listen to Otis Redding’s version of “A Change is Gonna Come,” featuring Steve Cropper on guitar. For photocell tremolo, try the Doors’ “Riders on the Storm.”)

Bluesman Big Bill Broonzy is probably the guitarist on several 1942 songs by singer/pianist Roosevelt Sykes. The tremolo effect is unmistakable.

Early Tremolo Recordings
With DeArmond tremolo boxes underway by 1941 and amplifiers incorporating tremolo circuits appearing by end of the decade, what are the earliest guitar tremolo recordings? Maybe a better question would be, why would DeArmond, Danelectro, or Gibson offer tremolo for guitar unless guitarists were experimenting with the effect? Since the Hammond company was using tremolo in its organs since the 1930s, the potential for early experimentation by guitarists certainly existed. With that thought in mind, I’ll share the oldest tremolo tracks I’ve uncovered so far. If you’re aware of earlier ones, please let us know

Guitar tremolo can clearly be heard on four songs that singer/pianist Roosevelt Sykes recorded in Chicago on April 16, 1942. “Are You Unhappy,” “You Can't Do That to Me,” “Sugar Babe Blues,” and “Love Has Something to Say” probably feature Big Bill Broonzy playing through a DeArmond unit.

Les Paul, electric guitar pioneer and mad scientist of the recording studio, may have used a subtle tremolo effect on his 1946 recording of “Sweet Hawaiian Moonlight.”

You can hear Muddy Waters playing through a tremolo effect on his 1953 song “Flood.” Two years later Bo Diddley made tremolo a centerpiece of his sound, using a DeArmond unit on his 1955 hits “Bo Diddley,” “Diddley Daddy,” and “Pretty Thing.”

By the late 1950s electric tremolo was in full swing. Duane Eddy famously incorporated it in many of his recordings. He obtained a DeArmond unit in 1957 and used it on “Rebel Rouser” the following year. According to Eddy, the tremolo effect was “cool because it was such a simple melody.” His other tremolo-based songs include “Stalkin’,” “Cannonball,” “The Lonely One,” and “Forty Miles of Bad Road.” Also in 1958, Link Wray recorded “Rumble,” where you can hear the effect being turned on in the final portion of the song.

The 1960s brought an entirely new wave of tremolo-infused amps, effect pedals, and guitar recordings—far more than we can cover here. But even a short list of great trem-fueled ’60s classics reveals how much the effect contributed to the decade’s sound.

• Slim Harpo, “Baby, Scratch My Back”

• Tommy James & the Shondells, “Crimson and Clover”

• The Shadows, “Apache”

• Buffalo Springfield, “For What It's Worth”

• Creedence Clearwater Revival, “Born on the Bayou”

• The Rolling Stones, “Gimme Shelter”

Let’s conclude our early history of tremolo with two songs that demonstrate how compelling tremolo can be: The Staple Singers 1956 recording of “Uncloudy Day” (above), with Pops Staples on guitar, and Nancy Sinatra’s “Bang Bang,” with L.A. session ace Billy Strange (below). Both songs feature vocals, tremolo guitar, and nothing else. When you have an effect this dramatic and powerful, who needs a band?