I am shifting from blues to jazz, and finding a number of songs use Eb or Dm chords. and I could use the D below the low E. It appears the band wants mainly walking lines improvised over the chords. I only have four string basses, so my options are: 1) just play the D where I have it available (lowest one on the A string), 2) shift the whole song (transcribe) up one octave, or 3) return my E string or all the strings down one full step(?). Comments on pros and cons of each solution? I don't really like retuning, although I have two basses so I can keep one tuned lower. I am not sure if running the D up higher one octave will ruin the walking line, although it seems in walking lines you sort of have to option to make jumps up or down as you wish as long as you keep the chord tones intact.