Two bass guitar pedals that more or less affect the bass in a subtle or complementary way are the bass equalizer pedal and the bass octave pedal.
Equalizer is another filter effect, because it involves altering parts of the audio signal’s frequency. Equalizer pedals have a set of control knobs that adjust a certain frequency range (a.k.a. bandwidth or band). There is a seperate control knob for each frequency range. The control knobs or sliders on an equalizer pedal look like the ones that are on a 1980’s stereo system, by the way. Most equalizer pedals have 7 bands, but some can have up to 10.
The knobs or sliders that control the lower bands obviously cut or boost your bass (as in low end frequency), the knobs/sliders in the center adjust mid frequencies, and the controls to the very right adjust the treble or high end frequencies. Equalizer pedals made just for the electric bass guitar, work extremely well with the instrument’s lower frequency range. As far as single-effect pedals go, equalizer pedals perhaps give you the most “room to work with” when it comes to shaping your sound.
An example of an effects pedal that has the ability to change (usually lower) your bass guitar’s pitch is the octave pedal. Octave pedals take the note that is being played and doubles it with a note that’s usually one or two octaves lower than the original note. Bass octave pedals are therefore, an ideal tool for bass players who want to thicken up their tone and solidify the low end. If you are doing a bass solo and are using an effects pedal that is causing your low end to get kind of lost, using an octave a pedal along with that other effects pedal would be the solution. You would be able to enjoy the effect of the other pedal, while not sacrificing the low end all thanks to the bass octave pedal.