We covered some rhythmic concepts a while back, and now I’m going to give you another simple yet powerful exercise that will improve your bass line creation as well as your soloing. Start with a simple eighth note rhythm, for instance a string of five eighth notes in a row (you can, and should, do this with other rhythms as well, but start with this simple example).
If you start on the downbeat, you’ll be playing eights from the “one” to the “three”. Play this on one note and make sure you’re comfortable with it. When you are, use it as the rhythm to play over a set of chords (as a bass line and as a solo), or even modally if you like.
When you’ve got this down, move the whole thing over one eighth note. Now you’re playing on the “and of one”, “two”, “and of two”, “three”, and “and of three”. This may feel unusual, as now you’re not playing the downbeat, but that’s the beauty of it, you’ll learn how to really vary your rhythmic phrasing.
As you no doubt see coming, the next thing to do is move it over another eighth, so now you’re starting on 2 and ending on four. Keep doing this until you’ve played this phrase on every beat of the measure. When you get to the second half, you’ll be phrasing over the bar line (for example, playing from the four through to the two of the next measure).
It’s good to do this with other rhythmic phrases as well. One way to do this (a way I did it) is take any bass line you want, reduce it to just its rhythm, and then start displacing it and improvising off those rhythms. You can also do this with triplet and sixteenth rhythms, and if you do it with odd time signatures, you should find that you’re playing in odd meters is much less stiff.