Musical and subtle sweetener. Used in the bright setting which is closest to the bypass tone.
Tried this into a clean Fender and dirtier el84 15watter.
Excels particularly into a Fender; does a subtle tightening of the bass and evens out the mids, giving the impression of a subtle upper mid boost. It is the best pedal I have used to date to follow a fuzz as it just takes an edge off the harshness. Clean sounds are nice but hard to distinguish as "better" (low mids are evened out and you may not like this) but the little bit of compression will help if you use it as a mild booster. Will do a nice mid boost into a Fender circuit too.
Into a warmer amp its less effective after fuzz and drive as the amp is doing some rounding off itself, however with one exception. The Buffalo td-x can be a bit raspy in the high end and the SP just takes it that bit closer to the smoothness of an ODR-1 without taking away too much attack. Worth it just for this if you are obsessive about lead tones.