Improvising over one chord for long stretches of time can be a musician's best friend or worst nightmare. With no harmonic variation, we are left to generate interest through our lines, phrasing, and creativity. When I started learning to improvise, a minor 7 chord and a Dorian mode were the only sounds that I wanted to hear at the time. I found it tremendously helpful to have the harmony stay in one spot while I mined for new ideas to play. Playing over a static chord was crucial in developing my sense of time and phrasing.