With three Reverb settings and three tremolo options as well, the Keeley Hydra brings a lot of versatility to these effect pedal staples.  For the reverb, the Hydra has spring, plate and room settings while the Tremolo offers harmonic, vibrato and sine wave.  You can take these options and mix & match them anyway you choose.  Each of the two footswitches control the reverb and tremolo respectively and each of the knobs has secondary functions, allowing in-depth control of each effect.  To round out the Hydra, it allows for three presets and tap tempo control.  There is also a range of options for output, including stereo and splitting the tremolo and reverb signals.  The Keeley Hydra expertly blends two related effects while allowing unrivaled independent control and routing.