Compression. It's the effect that's present on every piece of music you listen to, yet it's often forgotten when it comes to your pedalboard. A decent compressor can add sustain and attack to your notes, even out your dynamics for picking and boost your signal for solos.
MXR's new Custom Comp stompbox is straight outta the custom shop cased in MXR's familiar mini-housing. It's true bypass to avoid sucking your tone when you're not using it, and there are two controls, Output and Sensitivity, as well as an internal Attack control.
As you'd expect, the Output level controls the level, while Sensitivity sets the ratio or amount of compression you're applying, and the Attack controls how quickly the compressor kicks in. By setting the Output high, with lower Sensitivity levels, you can use the pedal for a subtle levelling of your dynamics or to give a boost. Turning up the Sensitivity starts to squash your sound more.
Although the Custom Comp is fairly unintrusive, you'll definitely be aware of its presence if you're liberal with your settings.
If you're playing a lot of high-gain sounds then you probably won't notice the Custom Comp's subtle low noise transparency, making £169 a pretty hefty outlay for just one pedal. Clean players after sharp sounds, however, will lap it up.