It's a dual pedal: a true vibrato + a hyper fuzz with 3 frequencies
Most amplifier have tremolos not true vibratos even though they claim to be vibrato.
You can find some vintage amps that deliver that but most don't this is a beautiful, well balanced vibrato that can be added to your playing anytime you choose.
You can also, without fear of overloading, add the Fuzz.
That particular fuzz can be extremely powerful uses the most usable frequencies to match your style.
And yes you can use the Fuzz only if you so desire.
The beauty and power of Shifty should complete your basic desires coming from a guitar pedal.
Strangely enough, bass players that have tried SHIFTY find it very usable when playing mood or psychedelic music or just plain fun parts.
The research on this pedal took close to a year to create at times very large expenses. The fine tunings have been frustrating but you will find it to be well worth it. We are very happy with the results and hope you will be too...