Brief History of Chorusing

by Phil Taylor

Phase Delay Chorus

Early chorusing and vibrato was achieved by means of a mechanical rotating speaker assembly - acoustically adding doppler phase-shifted signal to the original to produce phased chorus and tremolo effects. Although bulky, these systems are still much prized by blues players for their unique sound. The effect can be heard on Stevie Ray Vaughan’s "Cold Shot" and "Tin Pan Alley", which was created using a Fender Vibratone. Other users of the Vibratone include Pink Floyd ("Dark Side of the Moon"), Cream and Todd Rundgren.

During the 1960s transistorized electronic phase-shifters (like the Uni-Vibe) were developed as a compact and portable alternative. Although the Uni- Vibe was not an accruate speaker simulator, it did have its own unique character which players like Jimi Hendrix and Robin Trower ("Bridge of Sighs") used to great effect.

Time Delay Chorus

Time delay chorusing was first achieved with studio tape machines. By the 1970s miniaturization and integration of transistors made it possible to manufacture analog electronic bucket brigade delay line chips to do the same job, leading to wide-spread manufacture of compact chorus and flanger pedals. Digital delay hardware became available a few years later, followed more recently by digital modelling effects.

The Vibra Chorus

In the scheme of things the Vibra Chorus sits somewhere between Leslie/Fender Vibratone rotating speaker systems and the first electronic devices like the Uni-Vibe. So, in a way it's something that was missed along the evolutionary path of the chorusing effect. Its phase-shifting circuitry is optimized to operate on the frequency spectrum of electric guitar rather than the organ, where the Uni-Vibe attempted to simulate a Leslie rotating speaker system. This phase-delay chorusing is distinctly different from the analog timedelay based chorus pedals that were widely used during the 1980s and subjectively sounds more pleasing natural to the ear.