"A kick drum and a bass guitar pluck should have a very similar sound too. Both instruments require that you rid them of low midrange frequencies, like around 200Hz. Solo both and check to make sure that they are not killing each other. While a kick drum can get a little click sound for definition with a eq boost around 3 or 4KHz, the bass guitar will get articulation with a boost around 500-1000Hz. But both are going to have a similar 100Hz body to them, and pay very close attention to that. Also, don't get over-kill on the stuff below 100Hz. With most monitors, it is hard to hear anything below that, and you will have the tendency to boost 80Hz a lot to try to make these two instruments sound fuller. Be aware of that because a 3db eq boost on a kick drum at 80Hz is going to eat up a lot of your potential dynamic range in the mix, and it may not sound as good as you think once you start playing the song on home stereo systems "