We want to play phrases that are entertaining to listeners and have strong musical grounding. Since improvising a phrase is an instantaneous form of composition, one way to strengthen this area is to compose and write out phrases. We don’t necessarily want to use the composed line in our improvisation. Though if something we write is appealing enough then we may want to internalize the material.
Try taking a chord progression from your repertoire or one of your originals. We want to have about four bars. Analyze the progression, understanding how the chords relate to the tonic. Also look at how they are functioning at a given time. Are they suggesting a different key area?
Once you have looked at the progression think about rhythm and places, in time, where you might want to begin and end phrases. One approach is to pick a rhythm, write it out, then assign notes later. Whatever you decide, use a strong rhythm that is fairly dynamic.
Next, think about which guide tones you may want to use. Thirds and fifths are good starting and landing points. Mixing in other tones as well can help make the phrase more interesting. Remember tensions as well. The eleven, for example, is a strong tension on major chords.
As we take time with the composition process, understanding of harmony, melody and rhythm will increase. This will work to help the improvisations that we play in live situations. Consider taking time for composition.