Modeled after a coveted vintage compressor circuit (we can't tell which- either the Dyna-Comp or Ross), the H.B.E. CPR Compressor Retro is the type of effects pedal you may want on all the time. The CPR is an extremely transparent effect and it's quiet too- (won't add extra noise to your signal chain). Use it on any instrument to obtain singing sustain- Without the hiss, noise and annoyances associated with other compression pedals. The HBE CPR sounds best with an electric guitar though- straight into the front end of a tube amplifier. Raising the sustain control will increase the amount of compression and sustain from subtle to a poppy, percussive attack. The volume goes up as the sustain control is increased though, so you may have to adjust the level control accordingly. HomeBrew has really nailed it with the CPR. It's a great sounding compressor for electric guitar. Even people that don't normally like compressors seem to like the HBE Compressor Retro!